Journeyman Plumber (UPC/IPC) — All Questions

A horizontal 2 in fixture branch is installed at the code minimum slope. Over a developed run of 18 ft, how much total fall does the pipe have?

• a.9 in
• b.2-1/4 in
• c.1-1/8 in
• d.4-1/2 in✓

Pipe 2-1/2 in and smaller requires a minimum slope of 1/4 in per ft, so 18 ft x 1/4 in = 4-1/2 in of fall. 1-1/8 in comes from using 1/16 in per ft and 2-1/4 in from using the 1/8 in per ft rate that applies only to 3 in and larger pipe. 9 in would be 1/2 in per ft, which is double the required minimum.IPC §704.1

Under the Uniform Plumbing Code (UPC), what is the maximum developed length permitted between the trap weir and the vent opening for a 1-1/2 in trap arm?

• a.3-1/2 ft✓
• b.6 ft
• c.5 ft
• d.2-1/2 ft

UPC Table 1002.2 allows 3-1/2 ft (42 in) of developed length for a 1-1/2 in trap arm. Under the UPC, 2-1/2 ft is the limit for a 1-1/4 in arm, 5 ft applies to a 2 in arm, and 6 ft applies to a 3 in arm. Code divergence: the IPC (Table 909.1) is far more generous, permitting 6 ft for a 1-1/2 in arm, which is why the adopted code must be named rather than treating 3-1/2 ft as universal.UPC Table 1002.2

Except for traps specifically designed as deep seal traps, what is the required liquid seal depth of a fixture trap?

• a.2 in to 4 in✓
• b.1-1/2 in to 3 in
• c.2 in to 6 in
• d.1 in to 2 in

A standard fixture trap must hold a liquid seal of not less than 2 in and not more than 4 in. Seals shallower than 2 in evaporate or siphon away too easily, and a seal deeper than 4 in is classified as a deep seal trap, which is permitted only in specific applications, so the wider or shallower ranges are incorrect.IPC §1002.4

A 4 in building drain runs 96 ft from the last fixture connection to the point where it leaves the structure. Installed at the code minimum slope for its size, what is the total fall?

• a.6 in
• b.24 in
• c.48 in
• d.12 in✓

Drainage pipe 3 in and larger may be sloped at a minimum of 1/8 in per ft, so 96 ft x 1/8 in = 12 in of fall. 6 in results from using 1/16 in per ft, which is allowed only for 8 in and larger pipe where approved, and 24 in comes from applying the 1/4 in per ft rate used for 2-1/2 in and smaller pipe.IPC §704.1

A fixture drain serving a lavatory is 1-1/2 in in diameter. What is the smallest vent size that may serve it?

• a.1-1/2 in
• b.2 in
• c.1-1/4 in✓
• d.1 in

A vent must be at least one-half the diameter of the drain it serves but never smaller than 1-1/4 in. Half of 1-1/2 in is 3/4 in, so the 1-1/4 in floor controls. A 1 in vent violates the absolute minimum, while 1-1/2 in and 2 in are larger than required and are not the smallest permitted size. Both the IPC and UPC use this half-diameter, 1-1/4 in minimum rule, so the value is not code-divergent.IPC §906.2 / UPC §904.1

A horizontal building drain changes direction with a fitting that turns the flow 90 degrees. What does the code require at that point?

• a.A cleanout✓
• b.A backwater valve
• c.A relief vent
• d.An indirect waste receptor

A cleanout is required at each change of direction of the building drain or horizontal waste line that exceeds 45 degrees, because a 90 degree turn is the point most likely to trap a stoppage. A backwater valve protects against sewer backflow, a relief vent relieves pressure in a stack, and an indirect waste receptor handles unconnected discharge, so none of them satisfies the access requirement.UPC §708.1

A 2 in trap arm serves a floor-mounted fixture. The trap weir is at elevation 0. What is the greatest amount the trap arm may fall before it reaches the vent connection?

• a.1/2 in
• b.1-1/2 in
• c.2 in✓
• d.1 in

The trap arm may not fall more than one pipe diameter between the trap weir and the vent opening, so a 2 in arm may drop a maximum of 2 in. Any greater fall lets the crown of the arm flood and the fixture becomes self-siphoning. The smaller values correspond to diameters of other pipe sizes, not the 2 in arm in question. Both the IPC (§909.2) and UPC limit trap-arm fall to one pipe diameter, so this value is not code-divergent.IPC §909.2

Which trap arrangement is expressly prohibited because it will siphon its own seal?

• a.A P-trap vented within the permitted trap arm length
• b.An S-trap✓
• c.A drum trap serving a specialty fixture where approved
• d.A deep seal trap on a floor drain

An S-trap discharges vertically downward with no vent break, so the falling column of water pulls the seal out of the trap and is prohibited. A properly vented P-trap is the standard approved arrangement, and drum traps and deep seal traps remain permitted in specific approved applications.IPC §1002.1

A 3 in horizontal drain is run 72 ft at 1/8 in per ft. The invert at the upstream end is at elevation 100.00 ft. What is the invert elevation at the downstream end?

• a.99.90 ft
• b.99.25 ft✓
• c.99.85 ft
• d.98.50 ft

The fall is 72 ft x 1/8 in = 9 in, and 9 in equals 0.75 ft, so the downstream invert is 100.00 - 0.75 = 99.25 ft. The 99.85 ft and 99.90 ft answers understate the drop by treating the fall as inches of elevation rather than converting to feet, and 98.50 ft doubles the correct fall.

A vent terminal passes through a roof that is used only for weather protection in an area with no snow-depth requirement. What is the minimum height the vent must extend above the roof surface?

• a.3 in
• b.12 in
• c.6 in✓
• d.24 in

A vent through a roof used only for weather protection must extend at least 6 in above the roof. The 12 in dimension applies where the roof is used for any purpose other than weather protection, such as a deck or assembly area, and 3 in is below the minimum while 24 in exceeds what the code requires here.UPC §906.1

A vent terminal must be located away from an openable window. Which arrangement satisfies the code?

• a.6 ft horizontally from the window with the terminal 1 ft above the top
• b.11 ft horizontally from the window✓
• c.4 ft horizontally from the window with the terminal level with the sill
• d.8 ft horizontally from the window with the terminal at the same height

A vent terminal must be at least 10 ft horizontally from a door, openable window, or air intake, or else extend at least 3 ft above the top of that opening. At 11 ft the horizontal separation is satisfied outright. The other options fall short of 10 ft horizontally and none of them reaches 3 ft above the opening.UPC §906.2

Which fitting is acceptable for changing direction from horizontal to vertical in a drainage line?

• a.A sanitary tee installed on its back so flow enters horizontally
• b.A double sanitary tee serving back-to-back water closets on a 3 in stack
• c.A sanitary tee✓
• d.A short quarter bend on the horizontal branch alone

A sanitary tee is designed for horizontal-to-vertical direction change and is the standard approved fitting for that transition. A double sanitary tee is restricted where back-to-back water closets would discharge into each other on an undersized stack, a short quarter bend is not permitted for horizontal-to-horizontal or horizontal-to-vertical drainage flow, and a sanitary tee laid on its back obstructs flow and is prohibited.

Which fitting is required to change direction from horizontal to horizontal in a drainage line?

• a.A vent tee
• b.A sanitary tee
• c.A short sweep quarter bend
• d.A combination wye and 1/8 bend✓

A horizontal-to-horizontal change of direction must use a long sweep pattern such as a combination wye and 1/8 bend, which keeps the flow moving without a sharp shoulder where solids collect. A short sweep quarter bend turns too abruptly for horizontal flow, a sanitary tee is only for horizontal-to-vertical, and a vent tee is a dry vent fitting not rated for drainage flow.

A 4 in horizontal building drain runs 340 ft under a warehouse slab. Not counting the cleanout at the upstream end of the run, what is the minimum number of additional cleanouts required for spacing alone?

• a.2
• b.4
• c.6
• d.3✓

Horizontal drainage lines 4 in and smaller require a cleanout at intervals not exceeding 100 ft, so a 340 ft run needs cleanouts at roughly 100, 200, 300 ft and at the far end, which is 3 additional cleanouts beyond the upstream one to keep every interval at or under 100 ft. Two cleanouts would leave intervals longer than 100 ft, while 4 and 6 exceed the minimum the spacing rule requires.UPC §708.3.3

Under the Uniform Plumbing Code (UPC), a cleanout is installed on a 2 in horizontal waste line in a finished room. What is the minimum clearance required in front of the cleanout?

• a.12 in✓
• b.18 in
• c.6 in
• d.8 in

Under the UPC, cleanouts on pipe smaller than 3 in require at least 12 in of clearance in front of the opening for rodding, and pipe 3 in and larger requires 18 in, so a 2 in line needs 12 in. 6 in and 8 in are below any code clearance. Code divergence: the IPC (§708.8) instead requires 18 in of clearance for all pipe 6 in and smaller (36 in for 8 in and larger), so under the IPC the answer to this same rough-in would be 18 in — name the adopted code.UPC §707.4

A 6 in horizontal drainage line requires a cleanout. What is the minimum size of the cleanout opening?

• a.6 in
• b.3 in
• c.4 in✓
• d.5 in

A cleanout must be the same nominal size as the pipe it serves for pipe up to 4 in, and pipe larger than 4 in requires a cleanout of at least 4 in. A 6 in cleanout is larger than the code minimum, and 3 in and 5 in do not match either the same-size rule or the 4 in cap.

Under the UPC, where does the building drain end and the building sewer begin?

• a.2 ft outside the building wall✓
• b.At the property line
• c.At the face of the exterior wall
• d.5 ft outside the building wall

The UPC sets the boundary between building drain and building sewer at 2 ft outside the building wall, which is where the sewer designation and its materials rules take over. The exterior wall face and the property line are not the code dividing point, and the 5 ft dimension is the boundary used by some other model codes, not the UPC.

A single 3 in vent stack is 46 ft in developed length and serves a drainage stack. If the code limits a given vent size to a maximum developed length, exceeding that length requires which action?

• a.Sloping the vent at 1/4 in per ft
• b.Increasing the vent one pipe size for its entire developed length✓
• c.Reducing the vent one pipe size
• d.Installing a trap primer at the base

When a vent exceeds the maximum developed length permitted for its size, the vent must be increased one nominal pipe size for the entire developed length, not just the portion over the limit. Reducing the size makes the friction loss worse, a trap primer only replenishes trap seals, and vents are graded only enough to drain condensate back to the drain, which does not correct an over-length vent.

Two lavatories are installed back to back on opposite sides of a wall and discharge into the same double fitting at the same level. What vent arrangement is being used?

• a.A circuit vent
• b.A relief vent
• c.A common vent✓
• d.A wet vent

A single vent serving two fixture drains that connect at the same level into the same fitting is a common vent. A circuit vent serves a battery of fixtures on a horizontal branch, a relief vent provides additional air circulation between drain and vent systems, and a wet vent is a drain that also carries vent air for other fixtures.

A kitchen sink is located in an island counter where no wall is available for a conventional vent. Which venting method is designed for this condition?

• a.Vent stack rising to serve the whole drainage stack
• b.Circuit vent
• c.Island or loop vent✓
• d.Yoke vent

An island or loop vent rises as high as possible under the counter, returns downward, and then connects to a vent line, which is the method developed for fixtures with no adjacent wall. A circuit vent serves a battery of floor-set fixtures, a yoke vent relieves pressure between a drainage stack and its vent stack, and a vent stack is the vertical vent serving a whole drainage stack rather than a single island fixture.

An air admittance valve is used to vent an island sink. Which statement describes a correct installation?

• a.It may be buried in insulation inside a sealed wall cavity
• b.It relieves positive pressure in the drainage system
• c.It replaces the need for any vent open to the atmosphere in the building
• d.It must be accessible and located above the fixture trap weir✓

An air admittance valve must remain accessible for service and be installed above the trap weir of the fixture it serves, in a space with air available to the valve. It admits air only and does not relieve positive pressure, it cannot be sealed off inside insulation, and the building still requires at least one vent open to the atmosphere.IPC §917

What is the maximum vertical distance permitted between a fixture outlet and the trap weir serving that fixture?

• a.18 in
• b.36 in
• c.30 in
• d.24 in✓

The vertical drop from the fixture outlet to the trap weir may not exceed 24 in, which limits the velocity of falling waste that could otherwise scour the seal. 18 in is more restrictive than the code requires, and 30 in and 36 in exceed the permitted drop. The 24 in maximum is common to the IPC (§1002.1) and the UPC, so it is not code-divergent.IPC §1002.1

A commercial kitchen has a two-compartment sink whose drain must not connect directly to the sanitary drainage system. How must it discharge?

• a.Through an indirect waste with an air gap or air break into a receptor✓
• b.Through a directly connected trap and trap arm
• c.Through a double trap arrangement
• d.Through a backwater valve into the building sewer downstream of every other fixture connection

Fixtures that must be protected from sewage backflow discharge indirectly into an approved receptor through an air gap or air break so that no direct connection to the drainage system exists. A direct trap and trap arm connection defeats that protection, a backwater valve does not create the required physical separation, and double trapping of a fixture is prohibited outright.

A basement floor is below the elevation of the next upstream manhole on the public sewer. What device is required to protect the fixtures on that floor?

• a.A relief vent at the base of the stack
• b.A backwater valve✓
• c.An air admittance valve
• d.A trap primer

Fixtures on a floor below the next upstream manhole cover elevation must discharge through an accessible backwater valve so that a surcharged sewer cannot flood the low fixtures. An air admittance valve and a relief vent handle air pressure, not backflow, and a trap primer only keeps a trap seal from evaporating.UPC §710.0

A 3 in horizontal branch must gain 4-1/2 in of fall between two fixed points. At the minimum slope for 3 in pipe, what is the longest run that produces exactly that fall?

• a.36 ft✓
• b.54 ft
• c.24 ft
• d.18 ft

At 1/8 in per ft, a run of 36 ft yields 36 x 1/8 = 4-1/2 in of fall. The 18 ft answer uses 1/4 in per ft, which is the slope for 2-1/2 in and smaller pipe, and 54 ft and 24 ft do not produce 4-1/2 in at any code slope for 3 in pipe.

A 4 in horizontal drain is sized to carry a load of drainage fixture units. Which pipe run carries the greatest DFU load for a given diameter?

• a.A vent stack compared with a drainage stack of the same size
• b.A building drain sloped at 1/4 in per ft compared with the same drain at 1/8 in per ft✓
• c.A trap arm compared with a fixture branch of the same size
• d.A horizontal fixture branch compared with a building drain of the same nominal diameter and slope

For a horizontal drain of a given diameter, increasing the slope increases the carrying capacity, so a 4 in building drain at 1/4 in per ft is rated for more DFU than the same drain at 1/8 in per ft. A horizontal fixture branch is rated for fewer DFU than a building drain of equal size, a vent stack carries air rather than a DFU load, and a trap arm serves a single fixture.

A branch serves one water closet at 4 DFU, one lavatory at 1 DFU, one bathtub with shower at 2 DFU, and one kitchen sink at 2 DFU. What is the total DFU load on that branch?

• a.11 DFU
• b.9 DFU✓
• c.12 DFU
• d.7 DFU

The loads add directly: 4 + 1 + 2 + 2 = 9 DFU. Seven omits the kitchen sink, while 11 and 12 overstate the total by counting a fixture twice or by using a higher water closet value than the one given in the problem.

A horizontal fixture branch serves three lavatories only. Any branch that receives the discharge of a water closet must be at least what size?

• a.2 in
• b.3 in✓
• c.2-1/2 in
• d.1-1/2 in

No drain receiving the discharge of a water closet may be smaller than 3 in, regardless of how few fixture units are on it. The 1-1/2 in and 2 in sizes serve lavatories, sinks, and similar small fixtures, and 2-1/2 in is not a size used for water closet drainage.

Under the Uniform Plumbing Code (UPC), a 1-1/4 in trap arm serves a small lavatory. The vent is located 3 ft of developed length from the trap weir. What is the correct evaluation?

• a.Not acceptable, because a 1-1/4 in trap arm is limited to 2 ft
• b.Acceptable, because 1-1/4 in arms are exempt from the length table
• c.Not acceptable, because a 1-1/4 in trap arm is limited to 2-1/2 ft✓
• d.Acceptable, because any trap arm may run 5 ft

Under UPC Table 1002.2 the maximum developed length for a 1-1/4 in trap arm is 2-1/2 ft (30 in), so a 3 ft run exceeds the limit and the arm must be increased in size or the vent moved closer. No size is exempt from the table, and the 2 ft value understates the actual 2-1/2 ft UPC limit. Code divergence: the IPC (Table 909.1) permits 5 ft for a 1-1/4 in arm, under which a 3 ft run would pass, so the adopted code governs the answer.UPC Table 1002.2

A row of five lavatories on a common horizontal branch in a public restroom is vented by a single vent connected between the last two fixture drains. What type of venting is this?

• a.Common vent
• b.Individual vent
• c.Island vent
• d.Circuit vent✓

A circuit vent serves a battery of fixtures on a horizontal branch with one vent taken off ahead of the last fixture connection. A common vent serves only two fixtures connecting at the same level, an island vent is a loop arrangement for a fixture with no wall, and an individual vent serves one fixture drain.

An 8 in building drain is proposed at 1/16 in per ft over a 200 ft run. What is the fall, and is that slope permitted?

• a.6-1/4 in, and the slope is never permitted
• b.25 in, and the slope may be permitted for 8 in and larger pipe where approved
• c.12-1/2 in, and the slope may be permitted for 8 in and larger pipe where approved✓
• d.50 in, and the slope is never permitted

At 1/16 in per ft, 200 ft x 1/16 in = 12-1/2 in of fall, and slopes as flat as 1/16 in per ft may be approved for pipe 8 in and larger where the resulting velocity is adequate. The 25 in and 50 in figures come from applying the 1/8 in and 1/4 in rates, and 6-1/4 in halves the correct fall.

A bathroom group is arranged so that the lavatory drain also serves as the vent for the bathtub downstream of it. What is this arrangement called, and what limits it?

• a.A loop vent, limited to island sink fixtures that have no adjacent wall available
• b.A relief vent, limited to one fixture
• c.A wet vent, limited to the fixtures and sizes the code specifically allows✓
• d.A yoke vent, limited to stacks over 10 stories

A drain that carries waste from one fixture while also serving as the vent for other fixtures is a wet vent, and the code allows it only for the specific fixture combinations and minimum pipe sizes listed for wet venting. A relief vent is a dry vent that connects drain and vent systems, a yoke vent relieves pressure on tall stacks, and a loop vent is the island fixture arrangement.

Static pressure at the water meter reads 68 psi. The highest fixture served is 32 ft above the meter. Ignoring meter and friction losses, how much pressure remains at the elevation of that fixture?

• a.About 58.4 psi
• b.About 60.2 psi
• c.About 46.2 psi
• d.About 54.1 psi✓

Elevation loss is 0.433 psi for every foot of rise, so 32 ft x 0.433 = 13.86 psi, and 68 - 13.86 = 54.1 psi. The 60.2 and 58.4 answers come from using a smaller loss factor such as 0.25 or 0.3 psi per foot. The 46.2 answer wrongly applies 2.31 psi per foot, which is the inverse relationship (2.31 ft of head per psi).

How many feet of vertical head are equivalent to 22 psi of water pressure?

• a.About 9.5 ft
• b.About 22 ft
• c.About 50.8 ft✓
• d.About 45.4 ft

One psi equals 2.31 ft of head, so 22 x 2.31 = 50.8 ft. The 9.5 ft answer divides by 2.31 instead of multiplying, and 45.4 ft comes from using a rounded factor of 2.0 plus arithmetic error. Answering 22 ft ignores the conversion entirely and treats psi and feet as interchangeable.

A potable water supply outlet discharges over a receptor and the effective opening of the outlet is 1 in. What is the minimum required air gap?

• a.1-1/2 in
• b.2 in✓
• c.3 in
• d.1 in

The air gap must be at least twice the diameter of the effective opening, so 2 x 1 in = 2 in. The 1 in answer is only the code minimum floor that applies to very small openings, not the calculated value here. The 1-1/2 in choice uses a 1.5 multiplier and 3 in uses a 3x multiplier, neither of which the code uses.UPC §603.3.1

A supply outlet has an effective opening of 3/8 in. What minimum air gap must be provided above the flood level rim of the receiving vessel?

• a.2 in
• b.3/4 in
• c.1 in✓
• d.1-1/4 in

Twice the effective opening is 2 x 0.375 = 0.75 in, but the code sets an absolute minimum air gap of 1 in, so 1 in governs. The 3/4 in answer applies the 2x rule without checking the minimum. The 1-1/4 in and 2 in values are larger than anything the rule produces for a 3/8 in opening.IPC §608.15.1

A gauge on the building side of the meter shows a static street pressure of 96 psi with no flow. What does the plumbing code require?

• a.An approved vacuum relief valve installed on the water service ahead of the water meter assembly
• b.Nothing, because the pressure is still under 100 psi
• c.An approved pressure-reducing valve limiting downstream pressure to not more than 80 psi✓
• d.An increase of one pipe size on the water service

Where static pressure exceeds 80 psi, an approved pressure-reducing valve must be installed to hold the downstream distribution system at 80 psi or less. The 100 psi threshold does not exist in the code; 80 psi is the trigger. Upsizing pipe lowers friction loss but does nothing to static pressure, and a vacuum relief valve protects against collapse or siphoning, not high pressure.UPC §608.2

A 40 ft horizontal run of 3/4 in copper water tube is installed in a ceiling. Using a maximum horizontal support spacing of 6 ft for copper 1-1/2 in and smaller, what is the minimum number of hangers required?

• a.7 hangers✓
• b.5 hangers
• c.8 hangers
• d.6 hangers

40 ft divided by 6 ft equals 6.67 spaces, and since a partial space still needs a hanger you round up to 7. Answering 6 truncates the fraction and leaves a span longer than 6 ft. The 5 hanger answer assumes 8 ft spacing, and 8 hangers assumes the 5 ft spacing used for cast iron, not copper.UPC §313.3

A 24 ft horizontal run of 1/2 in CPVC water distribution pipe is supported at the maximum spacing of 3 ft. What is the minimum number of supports required?

• a.8 supports✓
• b.12 supports
• c.6 supports
• d.9 supports

24 ft divided by 3 ft equals 8 supports at the maximum allowed spacing. The 6 support answer uses the 4 ft spacing allowed for larger plastic pipe, and 12 supports assumes 2 ft spacing, which is more than the code requires. The 9 answer adds an extra support that the calculation does not produce.IPC Table 308.5

PEX tubing runs horizontally for 16 ft above a suspended ceiling. Using the maximum horizontal support spacing of 32 in for PEX, what is the minimum number of supports?

• a.6 supports✓
• b.3 supports
• c.5 supports
• d.4 supports

Convert first: 16 ft equals 192 in, and 192 divided by 32 equals 6 supports. The 4 and 3 answers come from using 48 in or 72 in spacing, which apply to rigid materials, not flexible PEX. Five supports would leave one span longer than 32 in and would allow the tubing to sag.IPC Table 308.5

To limit erosion-corrosion and noise, what is the generally accepted maximum design velocity in a copper hot water distribution line?

• a.8 feet per second
• b.10 feet per second
• c.12 feet per second
• d.5 feet per second✓

Hot water accelerates erosion of the copper tube wall, so hot lines are held to about 5 fps while cold lines are commonly designed to about 8 fps. The 8 fps answer is the cold water limit and is too aggressive for hot water. The 10 and 12 fps values are well above accepted design practice for any copper water line and would produce velocity noise and premature pinhole failures.

A commercial kitchen is being piped with solenoid-operated quick-closing valves on the dishwasher and ice machine supplies. What does the code require on those branches?

• a.A vacuum breaker on each supply branch
• b.A check valve installed immediately upstream of each quick-closing solenoid valve on the branch
• c.Approved water hammer arrestors sized and located per the manufacturer's instructions✓
• d.A larger supply pipe to slow the water velocity

Quick-closing valves stop flow almost instantly and convert momentum into a pressure spike, so the code requires approved water hammer arrestors on those branches. Upsizing pipe reduces velocity somewhat but does not satisfy the arrestor requirement. A check valve does not absorb the shock wave, and a vacuum breaker addresses back-siphonage, which is a different problem entirely.IPC §604.9

A potable water line supplies makeup water to a chemically treated boiler system and the connection is under continuous pressure. Which backflow prevention device is required?

• a.Hose bibb vacuum breaker
• b.Atmospheric vacuum breaker
• c.Double check valve assembly listed for continuous-pressure low-hazard service only
• d.Reduced pressure principle backflow preventer✓

Treated boiler water is a high hazard (health hazard) contaminant and the connection is under continuous pressure, which calls for a reduced pressure principle assembly. A double check assembly is only acceptable for low hazard, non-health, continuous pressure applications. An atmospheric vacuum breaker cannot be used under continuous pressure at all, and a hose bibb vacuum breaker is for hose outlets and protects only against back-siphonage.IPC §608.13

A fire sprinkler system with no antifreeze or chemical additives is connected to the potable water supply under continuous pressure. Which assembly is the appropriate minimum protection for this low hazard connection?

• a.Double check valve assembly✓
• b.Reduced pressure principle assembly
• c.Atmospheric vacuum breaker
• d.Pressure vacuum breaker

A non-additive sprinkler system is a low hazard (pollutant, not contaminant) connection under continuous pressure, which is the exact application for a double check valve assembly. A reduced pressure assembly exceeds the minimum required here and adds an unnecessary relief discharge. An atmospheric vacuum breaker may never be used under continuous pressure, and a pressure vacuum breaker protects against back-siphonage only, not back-pressure.IPC §608.13

An atmospheric vacuum breaker serves a fixture whose flood level rim is 34 in above the finished floor. What is the minimum height above the floor at which the vacuum breaker may be installed?

• a.40 in✓
• b.34 in
• c.46 in
• d.37 in

An atmospheric vacuum breaker must be at least 6 in above the flood level rim, so 34 + 6 = 40 in above the floor. Installing it at 34 in puts it level with the rim with no clearance at all. The 37 in answer uses a 3 in clearance and 46 in uses the 12 in clearance required for a pressure vacuum breaker above its highest outlet.IPC §608.13

A pressure vacuum breaker protects a lawn irrigation zone whose highest sprinkler head is 42 in above grade. What is the minimum height above grade for the vacuum breaker?

• a.4 ft 6 in✓
• b.3 ft 6 in
• c.4 ft 0 in
• d.5 ft 6 in

A pressure vacuum breaker must be at least 12 in above the highest downstream outlet, so 42 in + 12 in = 54 in, or 4 ft 6 in. The 3 ft 6 in answer is simply the head height with no clearance added. The 4 ft 0 in answer adds only 6 in, which is the atmospheric vacuum breaker rule, and 5 ft 6 in adds 24 in, more than the code requires.IPC §608.13

Which condition makes a pressure vacuum breaker an unacceptable choice for a given cross-connection?

• a.A booster pump downstream could push water back toward the supply✓
• b.The supply piping downstream of the device is copper tubing rather than galvanized steel
• c.The device would be located outdoors
• d.The outlet is a hose thread connection

A pressure vacuum breaker protects only against back-siphonage; a downstream pump creates back-pressure, which requires a double check assembly or reduced pressure assembly depending on the hazard level. Hose thread outlets, outdoor locations, and copper supply piping do not disqualify a pressure vacuum breaker. The distinction to remember is back-siphonage (negative supply pressure) versus back-pressure (higher downstream pressure).

Which copper tube designation has the heaviest wall thickness and is the type commonly required for an underground water service?

• a.Type L
• b.Type M
• c.Type DWV
• d.Type K✓

Wall thickness runs K heaviest, then L, then M, so Type K is specified where the tube is buried and exposed to soil and backfill loading. Type L is the common choice for interior water distribution and Type M is the thinnest pressure type, often restricted to above-ground use. Type DWV is not a pressure-rated water tube at all and is limited to drain, waste, and vent service.UPC §604.0

What is the maximum lead content permitted in solder and flux used on a potable water piping system?

• a.0.25 percent
• b.2 percent
• c.0.2 percent✓
• d.8 percent

Solder and flux used in potable water piping may not exceed 0.2 percent lead, which is why 50/50 tin-lead solder is prohibited. The 0.25 percent figure is a different limit, the weighted average lead content allowed on the wetted surfaces of pipe, fittings, and fixtures. The 2 percent and 8 percent values are far above any lead-free standard and describe legacy alloys no longer permitted.UPC §604.0

What is the maximum weighted average lead content permitted on the wetted surfaces of pipe, fittings, and fixtures used to convey water for human consumption?

• a.0.05 percent
• b.0.25 percent✓
• c.8 percent
• d.0.2 percent

The lead-free standard limits the wetted surfaces to a weighted average of not more than 0.25 percent lead. The 0.2 percent value is the separate limit that applies to solder and flux, not to the wetted surfaces of the components. The 0.05 percent figure is stricter than the code requires, and 8 percent describes older leaded brass that may no longer be installed in potable systems.

Static pressure at the main is 72 psi. Meter loss at design flow is 9 psi, the highest fixture is 26 ft above the meter, and 15 psi residual is required at that fixture. How much pressure is available to overcome friction loss in the piping?

• a.About 41.2 psi
• b.About 25.5 psi
• c.About 48.0 psi
• d.About 36.7 psi✓

Elevation loss is 26 x 0.433 = 11.26 psi, so 72 - 9 - 11.26 - 15 = 36.7 psi available for friction. The 48.0 psi answer forgets the required residual pressure, and 41.2 psi forgets part of the elevation loss. The 25.5 psi answer subtracts the residual twice or uses a 20 psi flushometer residual that this problem did not specify.UPC §610.0

A flushometer water closet on the top floor requires 20 psi residual. Static pressure is 65 psi, combined meter and backflow preventer loss is 10 psi, and the flush valve is 34 ft above the meter. How much pressure remains for friction loss in the piping and fittings?

• a.About 35.0 psi
• b.About 14.7 psi
• c.About 25.3 psi
• d.About 20.3 psi✓

Elevation loss is 34 x 0.433 = 14.72 psi, so 65 - 10 - 14.72 - 20 = 20.3 psi for friction. The 35.0 psi answer ignores the elevation loss, and 25.3 psi uses a 15 psi residual instead of the 20 psi a flushometer needs. The 14.7 psi choice is the elevation loss itself, not the friction allowance.UPC §610.0

A sizing problem leaves 24 psi available for friction loss. The measured developed length to the most remote fixture is 160 ft, and fittings are estimated to add 50 percent to that length. What is the allowable friction loss per 100 ft of pipe?

• a.About 6.7 psi per 100 ft
• b.About 10 psi per 100 ft✓
• c.About 24 psi per 100 ft
• d.About 15 psi per 100 ft

Total equivalent length is 160 x 1.5 = 240 ft, so 24 psi / 240 ft x 100 = 10 psi per 100 ft. The 15 psi answer divides by the measured 160 ft and skips the fitting allowance. The 6.7 psi answer overstates the equivalent length, and 24 psi per 100 ft simply restates the total budget without dividing by length.UPC §610.0

A dwelling unit contains one flush tank water closet (2.5 WSFU), two lavatories (1.0 WSFU each), one bathtub with shower (4.0 WSFU), one kitchen sink (1.5 WSFU), one dishwasher (1.5 WSFU), and one clothes washer (4.0 WSFU). What is the total water supply fixture unit load?

• a.16.5 WSFU
• b.15.5 WSFU✓
• c.14.5 WSFU
• d.13.0 WSFU

Adding the listed values gives 2.5 + 1.0 + 1.0 + 4.0 + 1.5 + 1.5 + 4.0 = 15.5 WSFU. The 14.5 answer counts only one lavatory, and 13.0 drops the dishwasher. The 16.5 answer adds an extra fixture unit that is not in the list; the total load is then carried into the sizing table to pick the service and distribution sizes.

Using the standard fixture unit to gpm conversion curve, what happens to the estimated demand when the total water supply fixture unit load on a system is doubled?

• a.The demand in gpm increases by less than double✓
• b.The demand in gpm more than doubles
• c.The demand in gpm exactly doubles
• d.The demand in gpm stays the same

The conversion curve is probability based: as more fixtures are added, the chance that all of them run at once drops, so gpm rises more slowly than fixture units. This diversity is why a 200 WSFU building does not need twice the flow of a 100 WSFU building. Assuming a straight-line doubling oversizes the service, and the more-than-double and no-change answers contradict how the curve behaves.IPC Appendix E

What is the minimum nominal size normally permitted for a water service pipe serving a building?

• a.5/8 in
• b.3/4 in✓
• c.1 in
• d.1/2 in

The water service pipe may not be smaller than 3/4 in regardless of what the fixture unit calculation produces. A 1/2 in service is below the code floor even for a very small single-fixture building, and 5/8 in is a meter size designation, not a standard pipe size. Requiring 1 in as the minimum is stricter than the code and would be a design choice, not a code requirement.

The highest fixture in a building is 28 ft above the meter and requires 15 psi residual. Meter loss is 5 psi and calculated friction loss in the piping is 12 psi. What minimum static pressure is needed at the meter?

• a.About 55.1 psi
• b.About 44.1 psi✓
• c.About 32.0 psi
• d.About 40.0 psi

Add every loss to the required residual: 28 x 0.433 = 12.12 psi elevation, plus 5 psi meter, plus 12 psi friction, plus 15 psi residual equals 44.1 psi. The 32.0 psi answer omits the elevation loss, and 40.0 psi rounds the elevation loss down to about 8 psi. The 55.1 psi answer double counts one of the losses and would call for a booster that is not actually needed.UPC §610.0

Using velocity (fps) = 0.408 x flow (gpm) divided by the square of the inside diameter (in), what is the velocity of 12 gpm flowing in 3/4 in Type L copper with an inside diameter of 0.785 in?

• a.About 10.2 fps
• b.About 6.0 fps
• c.About 4.4 fps
• d.About 7.9 fps✓

0.408 x 12 = 4.896, and 0.785 squared is 0.616, so 4.896 / 0.616 = 7.9 fps, right at the practical 8 fps cold water limit. The 4.4 and 6.0 answers come from dividing by the diameter instead of the diameter squared or from using the nominal 3/4 in size. The 10.2 answer uses a smaller inside diameter such as 0.69 in, which belongs to a heavier wall tube.

A 60 ft straight run of CPVC hot water pipe will see a 70 degree F temperature change. Using a coefficient of thermal expansion of 0.000034 in per in per degree F, approximately how much will the run expand?

• a.About 2.4 in
• b.About 1.7 in✓
• c.About 1.0 in
• d.About 0.6 in

Convert to inches first: 60 ft = 720 in, and 720 x 0.000034 x 70 = 1.71 in of movement, which is why an offset or expansion loop is needed. The 0.6 in and 1.0 in answers come from using only part of the temperature change or forgetting the foot-to-inch conversion. The 2.4 in answer uses a temperature change near 100 degrees F rather than the 70 degrees stated.

An existing galvanized steel water line is being extended with copper tube. What must be installed at the point where the two materials join?

• a.An approved dielectric fitting or dielectric union✓
• b.A rubber sleeve coupling with stainless steel clamps
• c.A soldered joint made directly to the steel pipe
• d.A brass compression coupling

Copper and galvanized steel are far apart on the galvanic scale, so a dielectric fitting is required to break the metallic path and prevent accelerated corrosion at the joint. A brass coupling still conducts and only shifts the corrosion cell rather than stopping it. Copper cannot be soldered directly to galvanized steel, and a rubber sleeve coupling is a drainage fitting that is not rated for water distribution pressure.IPC §605

A water closet is being roughed in against a side partition in a narrow alcove. Measuring from the finished face of the partition to the center of the closet outlet, what is the minimum dimension the model plumbing codes require?

• a.12 inches
• b.14 inches
• c.18 inches
• d.15 inches✓

The centerline of a water closet must be at least 15 inches from any side wall, partition, or vanity, which is what makes a 30 inch wide alcove the practical minimum for a single fixture. The 12 inch figure is the standard rough-in distance from the finished back wall to the closet flange center, not a side clearance. 14 inches and 18 inches are not code minimums; 18 inches is a common designer's comfort dimension and 14 inches is simply short of the requirement.IPC §405.3.1

Two water closets are to be installed side by side in a school restroom. What is the minimum distance between the centerline of one closet and the centerline of the adjacent closet?

• a.36 inches
• b.24 inches
• c.21 inches
• d.30 inches✓

Because each closet needs 15 inches of clearance on each side of its centerline, two adjacent closets require 15 plus 15, or 30 inches center to center. The 24 inch and 21 inches figures are front clearance numbers, not lateral spacing. 36 inches exceeds the requirement and would be an accessibility compartment width rather than the general fixture spacing minimum.

A framed water closet compartment measures 32 inches wide inside the finished surfaces, and the closet is set exactly on the center of that width. Does the installation satisfy the side clearance requirement?

• a.No, the centerline is only 15 inches from each side and 16 inches is required
• b.Yes, the centerline is 16 inches from each side, which exceeds the 15 inch minimum✓
• c.Yes, but only because a compartment is exempt from side clearance rules
• d.No, a compartment must be at least 36 inches wide in all cases

Half of 32 inches is 16 inches, so each side has 16 inches of clearance from the centerline, one inch more than the 15 inch minimum. The requirement is 15 inches, not 16, so the first choice reverses the numbers. Compartments are not exempt from clearance rules, and 36 inches is an accessible-stall dimension rather than a universal minimum.

Under the International Plumbing Code, what is the minimum clear space required in front of a water closet, measured from the front edge of the fixture to any wall or obstruction?

• a.24 inches
• b.15 inches
• c.21 inches✓
• d.30 inches

The IPC requires 21 inches of clear space in front of a water closet, lavatory, or bidet, although some jurisdictions and the UPC require 24 inches. 15 inches is the side clearance from the centerline, not a front dimension. 30 inches is the center-to-center spacing between two closets and has nothing to do with front approach space.IPC §405.3.1

A building owner replaces 40 old 3.5 gpf water closets with 1.28 gpf high efficiency models. If the fixtures are flushed a combined total of 2,000 times per day, how much water is saved per day?

• a.5,120 gallons
• b.3,500 gallons
• c.4,440 gallons✓
• d.2,560 gallons

The savings per flush is 3.5 minus 1.28, or 2.22 gallons, and 2.22 times 2,000 flushes equals 4,440 gallons per day. 2,560 gallons is 1.28 times 2,000, the new consumption rather than the savings. 5,120 and 3,500 gallons come from doubling the new usage or from using the old flush volume alone, neither of which is a difference calculation.IPC §604.4

A storage type water heater is being installed. Which device must be provided on the tank to protect against both excessive temperature and excessive pressure?

• a.A backflow preventer on the cold water inlet
• b.A vacuum relief valve at the top of the tank
• c.A pressure reducing valve on the building supply
• d.A combination temperature and pressure relief valve✓

Every storage water heater must be equipped with an approved combination temperature and pressure relief valve, typically rated to open at 210 degrees F and 150 psi. A vacuum relief valve prevents siphoning of the tank on bottom-fed heaters but does not relieve pressure or temperature. A backflow preventer and a pressure reducing valve address contamination and supply pressure, not tank overpressure or overheating.IPC §504.4

A temperature and pressure relief valve has a 3/4 inch outlet. Which discharge piping arrangement is acceptable?

• a.3/4 inch pipe running by gravity to terminate 8 inches above the floor with a plain end✓
• b.1/2 inch copper reduced at the valve and terminating 30 inches above the floor
• c.3/4 inch pipe with a threaded cap installed on the terminal end
• d.3/4 inch pipe with a ball valve installed for service isolation

Discharge piping must be full size of the valve outlet with no reduction, must drain by gravity, must have no valve in the line, and must terminate between 6 and 24 inches above the ground or an approved receptor with no threads on the end. The 1/2 inch option reduces the pipe and terminates too high, the ball valve option installs a prohibited shutoff, and the threaded cap option both threads the end and blocks discharge entirely.IPC §504.6

A 50 gallon water heater is installed in the attic above a finished ceiling. A drain pan is required. What is the minimum size of the pan drain line?

• a.3/4 inch✓
• b.1 inch
• c.5/8 inch
• d.1/2 inch

Where leakage would cause damage to the structure, a pan is required and its indirect drain must be at least 3/4 inch in diameter, discharging to an approved location. 1/2 inch and 5/8 inch are undersized and would not carry the flow of a leaking tank. A 1 inch pan drain is permitted as an upsize but is not the code minimum being asked for.IPC §504.7

A gas fired water heater is installed in a residential garage in a seismic zone. It must be strapped in two places. Where must the lower strap be located relative to the heater's controls?

• a.At least 4 inches above the controls✓
• b.At least 4 inches below the controls
• c.At the exact vertical midpoint of the tank
• d.Directly across the control housing

The two straps go around the upper third and the lower third of the tank, and the lower strap must be at least 4 inches above the controls so the strap does not damage or obstruct the gas valve and thermostat. Strapping across or below the controls interferes with service and with the control housing itself. A single midpoint strap does not satisfy the two-point bracing requirement.

The same gas water heater is installed in that garage on a concrete slab. What is the minimum height that the source of ignition must be elevated above the garage floor?

• a.18 inches✓
• b.24 inches
• c.12 inches
• d.6 inches

Ignition sources in a garage must be at least 18 inches above the floor because gasoline vapors are heavier than air and pool at floor level. 12 inches and 6 inches leave the burner inside the vapor layer. 24 inches is higher than required and is not the code figure, although a taller platform would still comply.

A 120,000 Btu/h gas water heater draws all of its combustion air directly from outdoors through two vertical ducts. Using the 1 square inch per 4,000 Btu/h rule for vertical ducts, what is the required free area of each opening?

• a.15 square inches
• b.12 square inches
• c.30 square inches✓
• d.60 square inches

Dividing 120,000 by 4,000 gives 30 square inches, and that is the required free area for each of the two openings, one near the top and one near the bottom of the enclosure. 60 square inches is the combined area of both openings, not the size of each. 15 square inches halves the correct figure, and 12 square inches corresponds to no recognized ratio.

A 100,000 Btu/h water heater is placed in a closet and will take combustion air from inside the building only. Using the rule of thumb of 50 cubic feet of room volume per 1,000 Btu/h, what minimum volume of communicating space is needed?

• a.10,000 cubic feet
• b.3,000 cubic feet
• c.5,000 cubic feet✓
• d.2,000 cubic feet

Dividing 100,000 by 1,000 gives 100, and 100 times 50 cubic feet equals 5,000 cubic feet of communicating volume. 2,000 and 3,000 cubic feet come from applying a 20 or 30 cubic foot factor that the standard indoor air method does not use. 10,000 cubic feet doubles the requirement and would only be relevant if two such appliances shared the space.

Where an enclosure takes combustion air from an adjacent room through two permanent openings, where must those openings be located?

• a.One opening at the ceiling and one located at any convenient height on an outside wall of the room
• b.Both within 12 inches of the ceiling of the enclosure
• c.One within 12 inches of the top of the enclosure and one within 12 inches of the bottom✓
• d.Both within 12 inches of the floor of the enclosure

The two-opening method requires one opening within 12 inches of the top and one within 12 inches of the bottom of the enclosure so that heated air can exhaust high while replacement air enters low. Placing both openings high or both low defeats the convective loop that drives the air exchange. Locating the lower opening at any convenient height does not satisfy the 12 inch dimension.

A shower compartment is framed 32 inches by 32 inches inside the finished walls. Does it meet the minimum area and minimum dimension requirements for a shower?

• a.No, the minimum interior dimension is 36 inches in every direction
• b.Yes, 1,024 square inches meets the area minimum and 32 inches exceeds the 30 inch dimension minimum✓
• c.No, the area works out to 1,024 square inches but a minimum of 1,200 square inches is required for a stall
• d.Yes, but only if a 30 inch wide door is installed

32 times 32 equals 1,024 square inches and each interior dimension of 32 inches clears the 30 inch minimum, so the stall complies. Code divergence: the UPC (§411.7) sets the minimum area at 1,024 square inches, which 32 by 32 meets exactly, while the IPC (§417.4) sets it lower at 900 square inches, so 1,024 clears both codes. The 1,200 square inch figure and a universal 36 inch interior dimension are not code minimums, and a shower door need only provide a 22 inch clear opening, so a 30 inch door is not what makes the stall compliant.UPC §411.7 / IPC §417.4

An indirect waste pipe from a commercial ice machine is 1-1/2 inches in diameter and discharges into a floor sink. What is the minimum required air gap?

• a.2 inches
• b.1 inch
• c.1-1/2 inches
• d.3 inches✓

The air gap for an indirect waste must be at least twice the effective diameter of the discharge pipe, so 2 times 1-1/2 inches equals 3 inches measured from the pipe outlet to the flood level rim of the receptor. 1 inch is only the absolute minimum air gap for very small pipes. 2 inches and 1-1/2 inches apply the wrong multiplier to the pipe size.IPC §802.2

A 3/8 inch indirect waste tube from a beverage dispenser discharges over an open receptor. Applying the air gap rule, what is the required air gap?

• a.3/8 inch
• b.3/4 inch
• c.1-1/2 inches
• d.1 inch✓

Twice the pipe diameter would be only 3/4 inch, but the code also sets an absolute floor of 1 inch, so the required air gap is 1 inch. The 3/4 inch answer applies the multiplier and ignores the minimum. 1-1/2 inches and 3/8 inch are not produced by either part of the rule.IPC §802.2

A laundry standpipe for a residential clothes washer is roughed in with the top of the standpipe 14 inches above the trap weir. Is the installation acceptable?

• a.Yes, any height is acceptable as long as the trap is vented
• b.No, the standpipe must be at least 24 inches and not more than 60 inches above the trap weir
• c.Yes, 14 inches is within the allowable range
• d.No, the standpipe must extend at least 18 inches and not more than 42 inches above the trap weir✓

A clothes-washer standpipe must be a minimum of 18 inches above the trap weir, so 14 inches is too short and the discharge is likely to back out of the pipe. Height is regulated regardless of venting, so the first choice is wrong. Code divergence is on the maximum: the IPC (§802.4) allows up to 42 inches while the UPC (§807.4) caps it at 30 inches; the 18 inch minimum is common to both codes, which is why 14 inches fails under either code. The 24 to 60 inch range in the second choice is not a code window under either code.IPC §802.4 / UPC §807.4

A showerhead is rated at the maximum allowable flow. A user showers for 8 minutes. Assuming the head flows at its rated maximum, how much water is used?

• a.12.0 gallons
• b.24.0 gallons
• c.17.6 gallons
• d.20.0 gallons✓

The maximum showerhead flow rate is 2.5 gpm at 80 psi, and 2.5 times 8 minutes equals 20 gallons. 17.6 gallons would result from a 2.2 gpm lavatory faucet rate, which does not apply to showerheads. 12 gallons uses a 1.5 gpm rate and 24 gallons uses 3.0 gpm, neither of which is the code maximum for a shower.IPC §604.4

A public restroom is fitted with metering faucets. What is the maximum volume of water each faucet may deliver per metering cycle?

• a.0.25 gallon✓
• b.1.0 gallon
• c.0.5 gallon
• d.0.125 gallon

Public metering faucets are limited to 0.25 gallon per metering cycle, which is a volume limit rather than a flow rate limit because the valve shuts itself off. 0.5 gallon and 1.0 gallon are urinal flush volumes, not faucet cycle volumes. 0.125 gallon is half the allowance and is not a code figure.

A closet flange is set on a wood subfloor before the finished tile is installed, and the installer plans to seal the closet to the flange. Which practice is correct?

• a.Seal the flange to the bowl with structural construction adhesive instead of using any mechanical fasteners at all, then set the bowl
• b.Rely on the closet bolts alone to hold the flange to the floor
• c.Set the flange on top of the finished floor, secure it to the structure with fasteners, and seal with a wax or approved gasket✓
• d.Set the flange below the finished floor and shim the bowl with wood blocks

The closet flange must rest on and be mechanically secured to the finished floor or structure, and the joint between the bowl horn and the flange is sealed with a wax ring or an approved elastomeric gasket. A flange set below the finished floor leaves a gap that the seal cannot reliably bridge, and shimming with wood blocks is not an approved support method. Adhesive does not replace fasteners, and closet bolts secure the fixture to the flange rather than the flange to the floor.

A restaurant installs a grease interceptor sized for 30 minutes of retention. If the connected fixtures produce a peak flow of 25 gallons per minute through the flow control device, what liquid capacity does the retention rule call for?

• a.250 gallons
• b.750 gallons✓
• c.1,500 gallons
• d.500 gallons

Retention volume equals flow rate times retention time, so 25 gpm times 30 minutes equals 750 gallons. 250 gallons corresponds to only 10 minutes of retention and 500 gallons to 20 minutes, both short of the design basis stated in the question. 1,500 gallons would represent a full hour of retention, twice what was specified.

A grease interceptor is inspected and found to contain accumulated grease and settled solids filling 25 percent of the total liquid depth. What action does the common maintenance standard require?

• a.Install a larger flow control device on the inlet to slow the incoming wash-water flow rate
• b.Pump and clean the interceptor, since the 25 percent threshold has been reached✓
• c.No action; cleaning is required only at 50 percent
• d.Add an enzyme treatment and re-inspect in six months

The widely used 25 percent rule requires that an interceptor be pumped when grease and solids occupy a quarter of the liquid depth, because beyond that point retention efficiency falls off sharply. Waiting for 50 percent allows grease carryover into the building drain. Enzyme or chemical treatments emulsify grease so it passes through the unit rather than being retained, and changing the flow control does not remove the accumulated material.IPC §1003.3

A residence has a pressure reducing valve with a check on the incoming water service, and the 40 gallon water heater's relief valve has begun weeping each evening. What is the most likely cause and the correct correction?

• a.The heater is oversized; reduce the thermostat to 90 degrees F
• b.The discharge line is too long; shorten it and add a threaded cap
• c.The relief valve is set too high; replace it with a 250 degree F valve
• d.Thermal expansion in a closed system; install an expansion tank sized for the system✓

A check or pressure reducing valve makes the system closed, so water expanding as it heats has nowhere to go and pressure rises until the relief valve lifts, which is corrected with a properly sized thermal expansion tank. Replacing the relief valve with a higher setting defeats the safety device rather than solving the pressure problem. Lowering the thermostat to 90 degrees F creates a bacterial growth risk, and capping the discharge line is expressly prohibited.

A three compartment pot sink and a food prep sink are being connected in a commercial kitchen. How must the waste from food handling equipment such as a food prep sink be connected to the drainage system?

• a.Directly connected but only through a grease interceptor
• b.Directly connected through a P-trap with no air gap or air break
• c.Indirectly connected through an air gap to an approved receptor✓
• d.Indirectly connected through an air break, which is acceptable for all food equipment

Waste from equipment in which food is stored, prepared, or handled must be indirectly connected by means of an air gap so that sewage cannot back up into food contact surfaces. A direct connection provides no physical break at all, even when a trap or interceptor is present. An air break relies on the pipe extending below the flood rim and is permitted for some indirect wastes but not for food handling equipment.IPC §802.1

A house is served with natural gas having a heating value of about 1,000 Btu per cubic foot. The connected appliances are a 100,000 Btu/h furnace, a 40,000 Btu/h water heater and a 35,000 Btu/h clothes dryer. What total flow, in cubic feet per hour, must the piping downstream of the meter carry?

• a.70 cfh
• b.175 cfh✓
• c.1,750 cfh
• d.132 cfh

Add the loads: 100,000 + 40,000 + 35,000 = 175,000 Btu/h, then divide by the 1,000 Btu per cubic foot heating value to get 175 cfh. 132 cfh is what you get if the dryer is left out or a propane figure is mixed in; 70 cfh comes from dividing by 2,500, which is the propane heating value; 1,750 cfh comes from dividing by 100 instead of 1,000.IFGC §402.4

The same 175,000 Btu/h total connected load is served by LP-gas instead of natural gas. Using about 2,500 Btu per cubic foot for propane, what flow must the piping carry?

• a.44 cfh
• b.437 cfh
• c.175 cfh
• d.70 cfh✓

For propane, cfh equals Btu/h divided by 2,500, so 175,000 / 2,500 = 70 cfh. 175 cfh is the natural gas answer using 1,000 Btu/cu ft; 437 cfh comes from multiplying instead of dividing by 2.5; 44 cfh comes from using a heating value near 4,000, which no common fuel gas has.IFGC §402.4

A natural gas system runs from the meter through section A (12 ft), then section B (18 ft), then section C (35 ft) to the farthest appliance. Using the longest developed length method, which length is used to select the size of section A?

• a.23 ft, the average of the three sections
• b.30 ft, the length from the meter through section B
• c.65 ft, the total length from the meter to the farthest outlet✓
• d.12 ft, the actual length of section A

The longest length method sizes every section of the system from the single length column that corresponds to the distance from the point of supply to the most remote outlet, here 12 + 18 + 35 = 65 ft. Using 12 ft or 30 ft applies a section length rather than the developed length to the farthest outlet and undersizes the pipe; averaging section lengths is not a recognized method.IFGC §402.4

Measured along the pipe, the most remote gas outlet in a building is 78 ft from the meter. Sizing tables are printed in 10 ft length increments. Which length row should be used?

• a.80 ft, the next length greater than the measured length✓
• b.78 ft, only if the table is redrawn to that value
• c.70 ft, because 78 is closer to 70 than to 90
• d.75 ft, by interpolating between rows

When the measured developed length falls between table rows, you use the next longer row, so 78 ft is sized from the 80 ft column. Rounding down to 70 ft would allow more pressure drop than the table assumes and undersize the pipe, and neither interpolating nor inventing a 78 ft row is permitted by the sizing method.IFGC §402.4

A residential natural gas system is supplied at about 7 in w.c. from the utility meter. Which allowable pressure drop is normally used with the standard low-pressure sizing tables for this system?

• a.0.5 in w.c.✓
• b.7 in w.c.
• c.11 in w.c.
• d.2 psi

Standard low-pressure natural gas sizing at roughly 7 in w.c. supply is based on an allowable pressure drop of 0.5 in w.c., which leaves enough pressure at each appliance regulator. 2 psi is the drop used for elevated-pressure systems with line regulators; 7 in w.c. is the delivery pressure itself, not the drop; 11 in w.c. is a typical LP-gas delivery pressure.

A gas furnace sits in a basement mechanical room. Its manual shutoff valve is installed in an adjacent storage room 9 ft away, behind a closed door. Why does this installation fail inspection?

• a.Only the single main shutoff valve located out at the gas meter is permitted to serve a furnace
• b.The valve must be downstream of the appliance regulator
• c.The shutoff must be within 6 ft of the appliance and in the same room as the appliance✓
• d.Shutoff valves must be within 3 ft of the appliance

Each appliance needs an accessible manual shutoff valve located in the same room as the appliance and within 6 ft of it, so a valve 9 ft away in another room is not acceptable. The 3 ft figure is a connector length limit, not a valve distance; a main valve at the meter does not satisfy the individual appliance shutoff; and the appliance shutoff belongs upstream of the appliance controls.IFGC §409.5

On which of the following appliances does the IFGC NOT require a sediment trap ahead of the appliance control valve?

• a.A clothes dryer✓
• b.A 100,000 Btu/h forced-air furnace
• c.A 40 gal storage water heater
• d.A gas-fired boiler

The IFGC exempts illuminating appliances, ranges, clothes dryers, decorative appliances, gas fireplaces and outdoor grills from the sediment trap requirement; a clothes dryer is on that list. Furnaces, water heaters and boilers all have gas control valves that must be protected, so each requires a trap located as close to the appliance inlet as practical.IFGC §408.4

A corrugated stainless steel tubing (CSST) gas system is installed in a two-story house. What is the minimum size of the copper bonding jumper used to bond the CSST system to the electrical service grounding electrode system?

• a.12 AWG
• b.10 AWG
• c.6 AWG✓
• d.14 AWG

CSST that is not listed as arc-resistant jacketed must be directly bonded with a jumper no smaller than 6 AWG copper, connected to a rigid metallic component of the gas piping upstream of the first CSST fitting. Smaller conductors such as 14, 12 or 10 AWG cannot reliably carry lightning-induced energy and would not satisfy the bonding requirement.IFGC §310

A new residential gas piping system will operate at a working pressure of 7 in w.c. (about 1/4 psi). What is the minimum test pressure required for the pressure test?

• a.10 psi
• b.3 psi✓
• c.0.375 psi, which is 1.5 times the working pressure
• d.1.5 in w.c.

The test pressure must be at least 1.5 times the proposed maximum working pressure but never less than 3 psi, and 1.5 times 1/4 psi is far below that floor, so 3 psi governs. The 0.375 psi and 1.5 in w.c. answers apply the multiplier while ignoring the 3 psi minimum; 10 psi exceeds what the code requires for this system.IFGC §406.4

The same 3 psi test is applied to the piping with a mechanical gauge. What is the minimum time the pressure must be held without any loss?

• a.10 minutes✓
• b.30 minutes
• c.24 hours
• d.5 minutes

The test duration must be at least 10 minutes, or longer if the code official or the size of the system requires it, with no drop in pressure. Five minutes is too short to satisfy the minimum, and 30 minutes and 24 hours exceed what the code requires for a standard residential test.IFGC §406.4.1

Which practice is correct when pressure testing a fuel gas piping system?

• a.Test with the fuel gas itself and check joints with an open flame
• b.Leave the appliance regulators connected in place so that they are tested together with the piping
• c.Use air, nitrogen or another inert gas and isolate appliances and regulators from the test✓
• d.Use oxygen so the test medium is dry and clean

The test medium must be air, nitrogen, carbon dioxide or another inert gas, and any equipment or regulator that cannot withstand the test pressure must be disconnected or isolated with a valve. Oxygen is prohibited because it reacts violently with pipe oils, appliance regulators are damaged by test pressures well above their rating, and locating leaks with a flame is never acceptable.IFGC §406.4

A gas range is connected with a listed appliance connector that runs 4 ft from the shutoff valve to the range. Which statement about this installation is correct?

• a.It is not allowed; no connector may exceed 3 ft
• b.It is allowed only if a second connector is added to reach the valve
• c.It is allowed only if the connector passes through the cabinet wall behind the range
• d.It is allowed, because ranges and clothes dryers may use connectors up to 6 ft long✓

Most appliance connectors are limited to 3 ft, but ranges and clothes dryers are permitted connectors up to 6 ft, so a 4 ft connector is acceptable. Connectors may not pass through walls, floors, ceilings or partitions, and connectors may not be joined together or reused, which rules out the other choices.IFGC §411.1

Which material is permitted for a buried gas service line running from an outdoor meter to a detached garage, but is prohibited for the piping inside the garage?

• a.Schedule 40 black steel pipe
• b.Polyethylene (PE) pipe✓
• c.Type L copper tube
• d.Corrugated stainless steel tubing

PE pipe is permitted only outside underground and must transition to an approved metallic material before it rises above grade or enters a building, and a tracer wire or other locating means must be buried with it. Black steel, CSST and copper (where the gas is not corrosive) are all approved for aboveground interior piping, so none of them are limited to underground use.IFGC §403

A 250 gal propane tank is filled to 200 gal of usable propane. At about 91,500 Btu per gallon, roughly how many total Btu of energy are stored?

• a.18,300,000 Btu✓
• b.457,500 Btu
• c.183,000,000 Btu
• d.1,830,000 Btu

Multiply 200 gal by 91,500 Btu per gallon to get 18,300,000 Btu. The 1,830,000 and 183,000,000 answers are the same digits off by a factor of ten, and 457,500 Btu comes from using the 2,500 Btu per cubic foot vapor value instead of the per-gallon liquid value.

A propane appliance with an input of 200,000 Btu/h runs continuously. Using about 91,500 Btu per gallon, about how long will 100 gal of propane last?

• a.About 92 hours
• b.About 46 hours✓
• c.About 4.6 hours
• d.About 23 hours

100 gal holds 9,150,000 Btu, and dividing by 200,000 Btu/h gives about 45.75 hours, or roughly 46 hours. The 23 hour answer doubles the burn rate, the 92 hour answer halves it, and 4.6 hours misplaces a decimal by a factor of ten.

A kitchen is served by a branch carrying only a 65,000 Btu/h range and a 40,000 Btu/h water heater, and that branch ends 15 ft from the meter, while the farthest outlet in the house is 90 ft from the meter. What load and what length are used to size this branch?

• a.175 cfh at 15 ft
• b.65 cfh at 90 ft
• c.105 cfh at 15 ft
• d.105 cfh at 90 ft✓

The branch carries 65,000 + 40,000 = 105,000 Btu/h, which is 105 cfh of natural gas, and under the longest length method every section is sized from the 90 ft distance to the most remote outlet. Using 15 ft applies the section length instead of the developed length; 65 cfh drops the water heater; 175 cfh adds load that this branch does not actually carry.

Gas piping passes through a concrete foundation wall below grade. What does the code require at that point?

• a.The pipe must be cast solidly and directly into the poured concrete foundation wall with no sleeve of any kind
• b.The pipe must be protected against corrosion and breakage, typically by a sleeve sealed at one end✓
• c.The pipe may be run through the wall only if it is PE
• d.A union must be installed inside the wall for future service

Piping that penetrates a foundation or exterior wall below grade must be sleeved and protected from corrosion and from stress caused by settlement, with the annular space sealed to prevent gas or water entry. Casting pipe directly into concrete invites corrosion and shear, joints and unions may not be concealed inside the wall, and PE is not permitted to enter a building.IFGC §404

A line pressure regulator is installed on a 2 psi system serving a residence. Which requirement applies to that regulator?

• a.The vent may terminate in any concealed space as long as it points down
• b.No downstream overpressure protection is needed at all here because the utility service regulator already handles every pressure condition on the line
• c.The regulator vent must terminate outdoors where it cannot be blocked, and a shutoff valve must be accessible upstream of the regulator✓
• d.The shutoff valve must be installed downstream of the regulator only

A line regulator that requires venting must have its vent piped to the outdoors, terminated to prevent water and insect entry, and an accessible shutoff valve must be located upstream so the regulator can be isolated for service. Venting into a concealed space would discharge gas inside the building on a diaphragm failure, and downstream overpressure protection is required in addition to any utility regulator.IFGC §410

A homeowner hires a plumbing company to replace a water heater and reroute the gas line to it. A journeyman employed by that company will perform the installation. Under a typical adopted plumbing code, who is authorized to apply for and hold the permit?

• a.Any journeyman on the crew, because the journeyman is the person who performs and signs off on the installation
• b.No one, because replacing an existing water heater is a like-for-like repair that never requires a permit
• c.The plumbing inspector, who issues the permit and holds it on the owner's behalf until the final approval
• d.The licensed plumbing contractor responsible for the work, or the owner of a single-family dwelling where the jurisdiction allows an owner-builder exemption✓

A permit is issued to the party who is legally responsible for the work, which is the licensed contractor, and many jurisdictions also allow an owner occupying a single-family home to pull a permit for work on that home. A journeyman performs the work under the contractor's license but is not the permit holder. The inspector enforces the code and approves the work; issuing a permit to himself would defeat that separation. Water heater replacement and any change to gas or water piping is permitted work, while truly minor items such as clearing a stoppage or swapping a faucet are the usual exemptions.IPC §106

Underground drainage piping is installed, and the crew backfills and compacts the trench before the groundwork inspection is called for. What does the code require?

• a.The concealed work must be uncovered and exposed for inspection, and the cost of uncovering and restoring it is borne by the permit holder✓
• b.A reinspection fee is paid and the buried piping is accepted as installed
• c.The inspector may simply carry the groundwork inspection over and then approve the already-buried piping later on at the rough-in inspection stage
• d.The work is accepted if the plumber photographed the piping and the joints before backfilling

Inspections follow a set sequence, typically groundwork or underground, then rough-in or top-out, then final, and no portion of the work may be covered or concealed until it has been inspected and approved. When work is covered early, the code allows the inspector to require it to be uncovered at the permit holder's expense. Photographs are not a substitute for the inspector's own examination and pressure test. Paying a reinspection fee covers the inspector's return trip; it does not buy approval of work no one has seen.IPC §107

Model plumbing codes are published on a three-year cycle. A state adopts one of those editions with statewide amendments, and a city then adopts the state code with additional local amendments. Which document governs an installation in that city?

• a.The manufacturer's installation instructions, which always supersede any adopted code
• b.The most recent model code edition published, whether or not the jurisdiction has adopted it
• c.The model code as published, because the local amendments only apply to commercial work
• d.The edition adopted by the jurisdiction, as amended, since a model code has no legal force until it is adopted✓

A model code is a template with no legal effect on its own; it becomes enforceable only when a state or local jurisdiction adopts it, usually with amendments that reflect local climate, soil and practice. The locally adopted amended edition therefore controls, and the authority having jurisdiction interprets it, with a board of appeals available to hear disputes over that interpretation. Newer published editions do not apply until adopted, which is why a jurisdiction may still be enforcing an edition several cycles old. Manufacturer instructions must be followed for listed and labeled products but cannot override an adopted code requirement.

A drainage, waste and vent system is being water tested. Which statement describes the test correctly?

• a.The system is filled to only a 5 ft head of water and held for just 5 minutes, and a small gradual drop in the level is acceptable as long as no active leak is actually visible anywhere on the piping run being examined by the inspector
• b.All openings are tightly plugged and the system is filled with water to at least a 10 ft head, except for the uppermost 10 ft of the system, and the water level is held for at least 15 minutes with no drop✓
• c.Only the piping below the lowest floor must be filled, and the water must stand for 30 minutes
• d.Water is run through each fixture for 15 minutes while the inspector watches the joints for drips

The water test plugs every opening, fills the system so that at least a 10 ft head of water stands on the section being tested, and requires the level to hold for a minimum of 15 minutes with no loss. The uppermost 10 ft of the system is the recognized exception, since there is no way to put a 10 ft head on the highest piping. A 5 ft head for 5 minutes is not a recognized test, and any drop in the water level means a leak, not an allowable tolerance. Running water through fixtures is a flow check, not a pressure test, and would not reveal a weeping joint under head.IPC §312.2

A high-rise DWV system is water tested in sections. The highest joint in the section currently under test is 28 ft above the building drain, and three more floors of piping continue above that section. To what height above the building drain must the test standpipe extend?

• a.33 ft
• b.38 ft✓
• c.30 ft
• d.28 ft, which is the height of the highest joint in the section under test

The test requires at least a 10 ft head of water on the highest point of the section being tested, so the standpipe must rise 10 ft above that point: 28 ft + 10 ft = 38 ft above the building drain. Stopping at 28 ft puts zero head on the top joint of the section, and 30 ft and 33 ft leave only 2 ft and 5 ft of head. The 10 ft exception for the uppermost portion of the system does not apply here because more piping continues above this section.IPC §312.2

Freezing weather makes a water test impractical, so the DWV rough-in is air tested instead. Which combination of test pressure and duration satisfies the code?

• a.50 psi held for 15 minutes
• b.10 psi held for 30 minutes
• c.5 psi, or a mercury column of 10 in, held for at least 15 minutes with no loss of pressure✓
• d.3 psi, or a mercury column of only 6 in, held for just 10 minutes before the plugs are pulled

The DWV air test uses a uniform gauge pressure of 5 psi, or the equivalent 10 in mercury column, maintained for at least 15 minutes without any drop. Three psi is below the required pressure and 10 minutes is short of the required duration. Ten psi and 50 psi are far above what a drainage system is intended to see; 50 psi is the water supply test value, not the DWV value, and that much air can blow test plugs out of a fitting.IPC §312.3

A water distribution system that will operate at 45 psi working pressure is tested with water. The plumber pumps it to 48 psi, and after 15 minutes the gauge reads 46 psi. How should the result be reported?

• a.Pass, because a small 2 psi drop over the 15 minute test window is within the normal allowable tolerance recognized for a pressurized water supply test on metallic pipe
• b.Pass, because the test pressure of 48 psi exceeded the 45 psi working pressure of the system
• c.Fail, because a water test must hold at not less than the system's working pressure for at least 15 minutes with no drop, and the pressure fell from 48 to 46 psi✓
• d.Fail, because a water supply system may only be tested with compressed air at 100 psi

Under IPC §312.5 the water-supply test is run at not less than the working pressure of the system and held for at least 15 minutes with no loss of pressure; any drop indicates a leak, so a 48 psi start that falls to 46 psi fails. There is no 50 psi floor on a water test: the 50 psi value in §312.5 applies only to the alternative air test permitted for piping other than plastic, not to the water test. Exceeding the working pressure alone (option b) is not a pass once the pressure drops, there is no allowable drop tolerance (option a), and 100 psi compressed air (option d) is not a required method.IPC §312.5

On a set of plumbing drawings, which view shows the vertical arrangement of the DWV piping, the floor-to-floor relationships and the order of the connections, drawn at an angle and generally not to scale?

• a.The floor plan view
• b.The riser or isometric diagram✓
• c.The civil or site utility plan
• d.The fixture schedule

A riser or isometric diagram is a single-line pictorial drawing of the system in three dimensions; it shows what connects to what and at what level but is not drawn to scale, so lengths cannot be measured off it. The floor plan is a scaled overhead view used to locate piping horizontally and to read symbols such as CW, HW, waste and vent. The site plan shows the sewer and water service outside the building along with invert elevations and benchmarks. The fixture schedule is a table of fixture types, models and connection sizes, not a view of the piping.

A floor plan is drawn at a scale of 1/4 in = 1 ft. A straight run of cold water piping measures 3-1/2 in on the drawing. What is the actual length of that run?

• a.3 ft 6 in
• b.17 ft 6 in
• c.14 ft✓
• d.10 ft 6 in

At 1/4 in = 1 ft, every full inch on the drawing represents 4 ft, so 3.5 in x 4 ft = 14 ft. Reading 3 ft 6 in simply repeats the measured inches as feet and ignores the scale entirely. Ten feet six inches comes from multiplying by 3 instead of 4, and 17 ft 6 in comes from multiplying by 5. Checking the answer the other way confirms it: 14 ft x 1/4 in per ft = 3.5 in on paper.

A site plan shows the invert elevation of a building sewer as 102.50 ft at the upstream end and 101.90 ft at the downstream end, with 48 ft of run between the two points. What is the slope of the sewer in inches per foot?

• a.0.125 in per ft
• b.0.15 in per ft✓
• c.0.10 in per ft
• d.0.0125 in per ft

The fall is 102.50 - 101.90 = 0.60 ft, which is 0.60 x 12 = 7.2 in, and 7.2 in divided by the 48 ft run gives 0.15 in per ft. The value 0.0125 is the slope expressed in feet per foot, not inches per foot, so it is off by a factor of 12. One tenth of an inch per foot would produce only 4.8 in of fall over 48 ft, and 0.125 in per ft, the familiar 1/8 in per ft grade, would produce 6 in of fall. Both are plausible-looking but leave the pipe higher than the plan calls for at the connection.

A building sewer runs 62 ft from the building drain to the connection at the main and is to be graded at 1/4 in per foot. The invert elevation at the upstream end is 100.00 ft. What is the invert elevation at the downstream end?

• a.98.45 ft
• b.99.35 ft
• c.98.71 ft✓
• d.101.29 ft

Total fall is 62 ft x 1/4 in per ft = 15.5 in, and 15.5 in divided by 12 is 1.29 ft, so the downstream invert is 100.00 - 1.29 = 98.71 ft. The value 98.45 uses 3/8 in per ft or rounds the fall to 18.6 in. The value 99.35 halves the fall, as if the grade were 1/8 in per ft, and 101.29 applies the fall in the wrong direction, which would run the sewer uphill toward the main.

A crew is setting sewer pipe in a trench 5 ft 6 in deep with vertical walls cut in previously disturbed soil. No sloping, shoring or shielding has been installed. What does OSHA require before a worker enters?

• a.Nothing, because a protective system is required only at 6 ft and greater
• b.The competent person may waive protection if the trench will be open for less than one work shift
• c.A protective system such as sloping, benching, shoring or a trench shield must be in place, because the excavation is 5 ft or more in depth✓
• d.A warning line set back from the top edge of the trench and a dedicated spotter watching the walls for movement are sufficient at this shallow depth

Employees in an excavation 5 ft deep or more must be protected by an adequate protective system, and the only exception is an excavation made entirely in stable rock. The 6 ft figure is a fall-protection threshold, not the trenching trigger. A warning line and a spotter do nothing to stop a wall from collapsing on someone standing in the trench. The competent person can require protection at less than 5 ft when there are signs of a cave-in hazard, but has no authority to waive it based on how long the trench will stay open.29 CFR 1926.652(a)(1)

A trench 7 ft deep with a 3 ft wide bottom is excavated in Type C soil and will be protected by sloping the walls at 1-1/2 to 1. How wide must the excavation be at the top?

• a.17 ft
• b.24 ft✓
• c.13 ft 6 in
• d.10 ft 6 in

Type C soil is sloped 1-1/2 horizontal to 1 vertical, about 34 degrees from horizontal, so each wall lays back 1.5 x 7 = 10.5 ft. Both walls are sloped, giving 3 + 10.5 + 10.5 = 24 ft at the top. The 13 ft 6 in answer adds the layback to only one side, and 10 ft 6 in is the layback of a single wall with the trench bottom left out entirely. Seventeen feet corresponds to a 1 to 1 slope, which is the ratio for Type B soil, not Type C.29 CFR 1926.652(b)

A trench 5 ft deep and 90 ft long is open, with workers spread along its full length installing pipe. What is the minimum number of ladders required and how must they be placed?

• a.Four, one for every 25 ft of trench length
• b.None is required, because a ladder or other means of egress is required only in trenches that are 6 ft deep or greater
• c.Two, placed so that no worker has more than 25 ft of lateral travel to reach a means of egress✓
• d.One, placed at the midpoint of the trench

Trenches 4 ft deep or more need a stairway, ladder, ramp or other safe means of exit located so that a worker travels no more than 25 ft laterally to reach it, so each ladder serves 25 ft in each direction, or 50 ft of trench. Ninety feet therefore needs two ladders, positioned so their 50 ft zones overlap and cover the whole length. The depth trigger is 4 ft, not 6 ft, so doing nothing is a violation. A single ladder at the midpoint leaves workers at the ends 45 ft from egress, and four ladders exceeds what the rule requires.29 CFR 1926.651(c)(2)

A trench must be excavated 22 ft deep in Type B soil to reach an existing sewer main. Which statement about the protective system and the excavated material is correct?

• a.Sloping is prohibited over 20 ft so only a trench box may be used, and the spoil must be kept 1 ft back
• b.The standard tabulated sloping tables may be used at essentially any depth, and the excavated spoil may simply be piled right at the trench edge where it serves as a convenient barrier
• c.The competent person may design the protective system on site at this depth, and the spoil must be kept 5 ft back
• d.A protective system for an excavation deeper than 20 ft must be designed by a registered professional engineer, and excavated material must be set back at least 2 ft from the edge✓

The tabulated sloping, benching and shoring options in the standard stop at 20 ft; anything deeper requires a protective system designed by a registered professional engineer. Spoil, tools and other surcharge loads must be kept at least 2 ft from the edge, or retained by a device that prevents material from falling in. Piling spoil at the edge adds load to the very wall that is most likely to fail, so it is never a barrier. A competent person inspects the excavation daily, before each shift and after rainstorms, but cannot substitute his own judgment for the engineered design a 22 ft trench requires.

Before anyone enters a 12 ft deep sewer manhole classified as a permit-required confined space, the atmosphere is tested and the meter reads 19.2 percent oxygen. What is the correct interpretation, and in what order must the atmosphere be tested?

• a.The reading is acceptable, and the correct order is toxics first, then oxygen, then flammables
• b.The reading is acceptable as long as the entrant wears a filtering facepiece respirator and an attendant is posted
• c.The reading indicates an oxygen-enriched atmosphere, and the correct order is flammables first, then oxygen, then toxics
• d.The reading is oxygen deficient, and the space must be tested for oxygen first, then flammable gases and vapors, then toxic contaminants✓

An acceptable atmosphere holds oxygen between 19.5 and 23.5 percent, so 19.2 percent is oxygen deficient and entry is prohibited until the space is ventilated and retested. Testing follows a fixed order of oxygen, then flammables, then toxics, because combustible gas sensors need oxygen to give a valid reading and a low oxygen result makes the flammability reading unreliable. An enriched atmosphere is above 23.5 percent, not below 19.5. A filtering facepiece only removes contaminants from the air; it cannot add oxygen, so it is never permitted in an oxygen-deficient space, which requires supplied air along with an attendant, a signed entry permit and a retrieval system.29 CFR 1910.146

A plumber is brazing copper joints in a finished mechanical room with combustible wood framing a few feet away. Which practice meets the fire prevention requirements for the work?

• a.A fire extinguisher is kept at the work area and a fire watch is maintained for at least 30 minutes after the torch is shut off✓
• b.The acetylene regulator may be set to 20 psig to speed up the braze as long as the cylinder is chained upright
• c.A fire watch is required only for welding, since brazing and soldering do not produce enough heat to start a fire
• d.Cylinders may be laid on their side while in use provided they are blocked so they cannot roll

Hot work requires suitable fire extinguishing equipment kept ready at the site and a fire watch maintained for at least 30 minutes after the work stops, because smoldering combustibles behind a wall or above a ceiling can take that long to flare up. Acetylene is unstable at pressure and must never be used above 15 psig at the torch. Brazing and soldering both use an open flame and easily ignite framing, insulation and dust, so the fire watch applies to them as well. Cylinders are stored, transported and used upright and secured so the valve cannot be broken off and the acetone in an acetylene cylinder is not drawn into the hose.29 CFR 1926.352

While replacing a section of galvanized water piping in a building from the 1950s, a plumber finds an adjacent steam line wrapped in crumbling fibrous insulation and sees that the old water joints were made with 50/50 tin-lead solder. What is the correct response?

• a.Disturb the crumbling insulation only while wearing an ordinary filtering facepiece dust mask, and reuse the old 50/50 tin-lead solder on the new joints so that they match the rest of the existing system throughout the building
• b.Leave the suspect asbestos insulation undisturbed, stop work in that area and notify the employer or building owner so a licensed abatement contractor can assess it, and make the new joints with lead-free solder✓
• c.Cut the insulation off with a utility knife, bag it, and continue with the repair
• d.Wet the insulation before removing it, since wetting eliminates the need for a licensed abatement contractor

Deteriorating pipe insulation in a building of that era is presumed asbestos-containing until sampling proves otherwise, and the correct action is to leave it alone, keep others out of the area and report it so licensed abatement personnel handle the removal. Cutting, scraping or wetting it yourself still releases fibers and does not make an untrained worker an abatement contractor, and a filtering facepiece does not authorize the work either. On the piping side, 50/50 tin-lead solder is prohibited in potable water systems; solder and flux must be lead free, and wetted surfaces of pipe, fittings and fixtures must not exceed a weighted average lead content of 0.25 percent.

In a jurisdiction served by separated (not combined) sewers, how must storm water from a roof drain be handled?

• a.Conveyed by a storm system kept fully separate from the sanitary drainage to an approved storm sewer or dry well✓
• b.Discharged into the sanitary building sewer at a point downstream of every plumbing fixture on the site
• c.Combined with the sanitary waste inside the building and then mechanically separated again at the street main
• d.Routed through the trap of the nearest plumbing fixture so that the added flow keeps that trap seal full

Storm water must not drain into a sewer intended for sewage only; the storm system is kept separate and discharged to an approved storm sewer, watercourse, dry well, or grade. Dumping roof water into the sanitary sewer overloads it and the treatment plant, running storm water through a fixture trap is not a drainage method, and only legacy combined sewers accept both, which new separated systems prohibit.IPC §1101.3 / UPC §1101

A roof-drain sizing table is based on a rainfall rate of 4 in/hr. The local design rainfall rate is 6 in/hr. A vertical conductor the table rates for 4,800 sq ft of roof area at 4 in/hr may actually serve how much roof area at the local 6 in/hr rate?

• a.3,200 sq ft✓
• b.4,800 sq ft
• c.7,200 sq ft
• d.2,400 sq ft

Allowable roof area scales inversely with rainfall rate: table area x (table rate / local rate) = 4,800 x (4/6) = 3,200 sq ft. Multiplying by 6/4 gives 7,200 sq ft, which oversizes the served area and undersizes the pipe. 4,800 sq ft ignores that the heavier local storm reduces capacity, and 2,400 sq ft halves the area with no basis.IPC §1106 (rainfall adjustment)

Under the IPC method, when a vertical wall drains onto an adjacent roof, how much of that wall's area is added to the projected roof area used to size the roof drainage?

• a.100 percent of the wall area
• b.50 percent of the wall area✓
• c.25 percent of the wall area
• d.None of the wall area

The IPC adds 50 percent of a single adjacent vertical wall's area to the horizontal roof projection, because wind drives only part of the rain off the wall onto the roof. Adding 100 percent overstates the runoff, adding nothing ignores a real load, and 25 percent is not the code figure. This value is IPC-specific; the UPC handles wall runoff with its own rules, so cite the adopted code.IPC §1106.4

A roof is surrounded by a parapet and drained only by interior roof drains. What does the code require so that a clogged primary drain cannot pond water and overload the roof?

• a.Nothing beyond a schedule to clean and rod the primary roof drains at least once every year
• b.A backwater valve on the primary roof conductor to stop water from rising back onto the roof
• c.A single primary conductor enlarged to carry roughly twice the design rainfall so no overflow is needed
• d.A secondary overflow roof drainage system, independent of the primary, discharging where it is readily seen✓

Where a parapet or other construction can impound water, a secondary or emergency overflow roof drainage system separate from the primary system is required, discharging to a point where its flow is readily seen as a warning that the primary is blocked. Cleaning schedules, a larger single conductor, and a backwater valve do none of this; the whole point is a fully independent backup path.IPC §1108 / UPC §1101.12

Where separate overflow (secondary) roof drains are installed, at what elevation is the overflow drain inlet or scupper typically set relative to the low point of the roof?

• a.Flush with the low point of the roof
• b.At the top of the parapet wall
• c.2 inches above the low point of the roof✓
• d.6 inches above the low point of the roof

The secondary drain inlet (or scupper opening) is set about 2 inches above the low point of the roof so the primary system carries all normal flow and the overflow acts only when water backs up. Setting it flush would let both systems share normal flow and mask a clogged primary, at the parapet top it would never relieve in time, and 6 inches allows too deep a pond before relief.IPC §1108 / §1107

A 4 in horizontal storm drain is sized like a sanitary building drain for slope. What is its minimum permitted slope?

• a.1/8 inch per foot✓
• b.1/16 inch per foot
• c.1/2 inch per foot
• d.1/4 inch per foot

Horizontal storm drains follow the same slope minimums as sanitary drains, and pipe 3 inches and larger may run at a minimum of 1/8 inch per foot, with the carrying capacity then read from the storm table at that slope. 1/16 inch per foot is only allowed for very large pipe where approved, while 1/4 and 1/2 inch per foot are steeper than the minimum being asked for.IPC §1106 / §704.1

Subsoil (foundation perimeter) drains that cannot drain by gravity to the storm system must discharge in what manner?

• a.Tied directly into the sanitary building drain along with the fixture waste
• b.Discharged into the trap of the nearest floor drain inside the building
• c.Connected to the building drain just downstream of an approved backwater valve
• d.Collected in a sump and pumped to an approved storm-water discharge point✓

Subsoil drains are collected in a sump and pumped to an approved storm-water discharge when gravity flow is not available. They may not be tied into the sanitary drainage, a floor-drain trap is not a legal collection point, and connecting downstream of a backwater valve still puts clear ground water into the sanitary system, which the code prohibits.IPC §1112 / UPC §1101.4

A horizontal fixture branch serves two showers at 2 DFU each, one floor drain at 2 DFU, and one clothes-washer standpipe at 3 DFU. What is the total drainage fixture unit load on the branch?

• a.7 DFU
• b.9 DFU✓
• c.11 DFU
• d.8 DFU

The loads add directly: 2 + 2 + 2 + 3 = 9 DFU. Seven drops the floor drain, eight uses 2 DFU for the clothes washer instead of the 3 given, and eleven adds a fixture unit that is not in the list. The total is then carried into the drain-sizing table to select the branch diameter.

A combination drain and vent (combination waste and vent) system is intended primarily for which fixtures?

• a.Water closets and urinals grouped together in a public restroom battery
• b.Only those fixtures that happen to sit on the topmost floor of a multistory building
• c.Any fixture at all, because an oversized horizontal drain is said to vent itself
• d.Floor drains, sinks and standpipes where a vertical vent cannot be run, but not water closets✓

A combination waste and vent system uses an oversized horizontal drain to provide air movement for fixtures such as floor drains, sinks, lavatories and standpipes where a conventional vertical vent cannot be run, and water closets are specifically not permitted on it. It is not limited to the top floor, and the claim that any oversized drain self-vents every fixture is false; the sizes and fixture types are strictly limited.IPC §915 / UPC §909

A floor drain in a rarely used mechanical room repeatedly loses its trap seal and emits sewer gas. What is the correct remedy?

• a.Add a trap primer or approved trap-seal protection device to keep the seal filled✓
• b.Pull the trap out so the floor drain runs open directly to the drainage piping
• c.Add a second trap in series below the first to build a deeper combined seal
• d.Cap and abandon the floor drain permanently so the seal cannot be lost again

A seldom-used trap loses its seal to evaporation, so the fix is a trap primer or listed trap-seal protection device that periodically adds water. Removing the trap opens a direct path for sewer gas, a second trap in series is prohibited double trapping, and permanently capping the drain removes required drainage rather than solving the seal loss.IPC §1002.4 / UPC §1007

Installing two traps in series on a single fixture drain is:

• a.Required whenever the fixture served is classified as a high-hazard connection
• b.Permitted without limit as long as both traps are exactly the same nominal size
• c.Required on any fixture drain that is larger than 3 inches in diameter
• d.Prohibited, since the unvented air between the seals blocks flow and can siphon both✓

Double trapping is prohibited: the air trapped between the two seals has no vent, so it resists flow and the fixture drains sluggishly while both seals are prone to siphon. It is never required by hazard or pipe size; a single properly vented trap is the correct arrangement for any fixture.IPC §1002.7 / UPC §1004

A sewage ejector pit that receives discharge from a below-grade water closet must be:

• a.Left open to the room so the pump and floats can be serviced easily
• b.Vented only through the pressurized pump discharge line leaving the pit
• c.Sealed gas-tight with a separate vent piped to the open air✓
• d.Cross-connected to the building storm drainage system for overflow

A pit handling sewage must have a gas-tight, sealed cover and a separate vent to the outdoors so sewer gases cannot enter the building and so air can move as the pit fills and empties. An open pit releases sewer gas, the pressurized discharge line cannot serve as a vent, and sewage may never be routed into the storm system.IPC §712 / UPC §710

What backflow protection is required on a typical residential exterior hose bibb (sillcock)?

• a.A listed hose-connection (atmospheric) vacuum breaker, nonremovable once installed✓
• b.A reduced-pressure principle backflow assembly on the branch feeding the sillcock
• c.A double check valve assembly installed ahead of the exterior wall penetration
• d.No device at all, since a garden hose is treated as a low-hazard connection

A hose bibb can be connected to a hose left in a pool of contaminated water, so it requires a listed hose-connection vacuum breaker to stop back-siphonage. A reduced-pressure assembly or double check is far more device than a single sillcock needs and is not the specified protection, and leaving it unprotected ignores a recognized cross-connection.IPC §608.15.4 / UPC §603

Where a water service pipe is laid near or in the same trench as the building sewer, the code requires:

• a.No separation is needed at all because both the water service and the sewer are pressure-rated pipes
• b.The sewer is laid above the water service so the potable water stays cooler in summer
• c.Both pipes are strapped tightly together in the trench so they share a single support
• d.The water service at least 12 inches above the sewer, on undisturbed earth, with the required setback✓

To keep sewage from contaminating the potable line if the sewer leaks, the water service must sit on solid undisturbed earth at least 12 inches above the top of the sewer, with a required horizontal separation (commonly 5 feet, but confirm the adopted code). Placing the sewer above the water service inverts the protection, no separation invites contamination, and strapping the pipes together defeats the vertical offset entirely.IPC §603.2 / UPC §720

Under the standard minimum fixture-supply table, what is the minimum nominal supply pipe size for a flushometer-valve water closet?

• a.3/8 inch
• b.1 inch✓
• c.1/2 inch
• d.3/4 inch

A flushometer water closet draws a very high instantaneous flow and requires a minimum 1 inch supply. A 3/8 inch supply serves a flush-tank water closet, 1/2 inch serves a lavatory or sink, and 3/4 inch is the minimum for a flushometer urinal, so each smaller size belongs to a different fixture.IPC Table 604.5 / UPC Table 610.4

Which joining method is NOT approved for PEX water tubing?

• a.Solvent-cement welded joints✓
• b.Insert fittings with copper crimp rings
• c.Cold-expansion fittings
• d.Insert fittings with stainless steel cinch clamps

PEX is joined only with mechanical fittings: cold-expansion, copper crimp rings, or stainless cinch clamps, all made to the listed PEX fitting standards. Solvent cement chemically fuses PVC, CPVC and ABS but does nothing to cross-linked polyethylene, so a solvent-welded PEX joint is not a recognized connection and would fail.IPC §605 / UPC §604

The minimum depth of cover (bury) for a water service pipe is governed primarily by:

• a.The local frost-line depth set by the authority having jurisdiction, to prevent freezing✓
• b.A single universal figure of 12 inches of cover required by every plumbing code
• c.A single universal figure of 6 feet of cover applied in every climate zone
• d.The pipe material by itself, independent of the local climate or frost depth

Burial depth is set by the local frost line so the service does not freeze, which is why the required cover differs sharply between a warm-winter region and a cold one. There is no single universal depth such as 12 inches or 6 feet, and the material of the pipe does not determine how deep freezing reaches; always confirm the depth with the authority having jurisdiction.IPC §305.4 / UPC §609

A vehicle repair garage has floor drains that may receive oil and flammable liquids. Before that drainage enters the sanitary system it must pass through:

• a.A hydromechanical grease interceptor sized for the fixtures
• b.A standard P-trap on each floor drain and nothing more
• c.A backwater valve set in the garage floor-drain line
• d.An oil (oil-and-sand) interceptor or separator✓

Drainage that can carry oil, gasoline or other flammable and volatile liquids must pass through an oil (oil-and-sand) interceptor so those liquids are separated out and kept out of the sewer, where they are a fire and pollution hazard. A grease interceptor is for animal and vegetable fats from kitchens, a plain P-trap and a backwater valve provide no separation of the oil at all.IPC §1003.4 / UPC §1017

Which discharge is prohibited from passing through a hydromechanical grease interceptor?

• a.A commercial three-compartment pot-and-pan wash sink
• b.A commercial pre-rinse sink ahead of the dishmachine
• c.A food-waste grinder (disposer) and water-closet waste✓
• d.A wok-range scupper drain in the cook line

A hydromechanical grease interceptor is sized for grease-laden wash water, and food-waste grinder discharge and any water-closet (sanitary) waste are prohibited from it: ground food overwhelms and blinds the unit, and sewage has no business in a grease device. Pot sinks, pre-rinse sinks and wok drains are exactly the grease-bearing fixtures the interceptor is meant to serve.IPC §1003.3.1 / UPC §1014

A bathtub-shower combination must be provided with what device to guard bathers against scalding?

• a.A vacuum breaker mounted on the showerhead outlet arm
• b.A pressure-balancing or thermostatic mixing valve limited to about 120 degrees F✓
• c.A check valve installed on the hot-water supply to the valve body
• d.A simple two-handle mixing faucet that provides no maximum outlet temperature stop whatsoever

Tub-shower valves must be pressure-balancing, thermostatic, or a combination type set to a maximum outlet of about 120 degrees F, so a sudden pressure change elsewhere cannot send scalding water to the bather. A vacuum breaker addresses backflow, a check valve addresses cross-flow, and a plain two-handle mixer offers no scald protection at all.IPC §424.3 / UPC §408

Hot water supplied to a public hand-washing lavatory must be limited (tempered) to a maximum temperature of:

• a.140 degrees F
• b.120 degrees F
• c.90 degrees F
• d.110 degrees F✓

Public lavatory hot water must be tempered to a maximum of 110 degrees F, typically with a listed tempering (mixing) valve, to prevent scalding of users who cannot control the supply. 140 degrees is a common storage temperature at the heater, 120 degrees is the tub-shower outlet limit, and 90 degrees is low enough to encourage bacterial growth and is not the code figure.IPC §416.5 / §607

Under the maximum water-use limits adopted by the model codes, the maximum flush volume for a wall-hung urinal is:

• a.0.5 gpf✓
• b.1.0 gpf
• c.1.6 gpf
• d.3.5 gpf

A urinal is limited to 0.5 gallon per flush. 1.6 gpf is the maximum for a water closet, 1.0 gpf describes older urinals no longer permitted new, and 3.5 gpf is a pre-1994 water-closet volume that the water-conservation limits eliminated.IPC §604.4 (EPAct)

A residential dishwasher drain must be protected against backflow of drain water by:

• a.A spring check valve concealed inside the sink base cabinet
• b.A direct low connection to the trap arm underneath the sink
• c.An approved air-gap fitting, or a high loop where the code allows it✓
• d.A grease interceptor placed on the dishwasher drain line

The dishwasher drain must have an approved air-gap fitting, or a high loop where the adopted code permits it, so that a sink stoppage cannot back dirty water into the dishwasher; note the UPC specifically requires an air-gap device, so confirm the local code. A concealed check valve is not an approved method, a direct low connection allows back-flooding, and a grease interceptor is unrelated to this backflow path.IPC §409.2 / UPC §807.4

Fuel gas piping is prohibited from being installed in or passing through which of the following?

• a.An unfinished basement used only for mechanical equipment
• b.A circulating air duct, a chimney or vent, or an elevator shaft✓
• c.An accessible attic space above the top-floor ceiling
• d.An exterior above-grade wall of a heated building

Gas piping may not run through circulating air ducts, clothes chutes, chimneys or gas vents, or elevator and dumbwaiter shafts, because a leak there would spread gas through the building or the pipe would be exposed to flue products or moving equipment. Basements, accessible attics and walls are normal, permitted routes when the piping is properly supported and protected.IFGC §404

Horizontal 3/4 inch steel gas pipe must be supported at intervals not exceeding:

• a.6 ft
• b.10 ft
• c.12 ft
• d.8 ft✓

Steel gas pipe of 3/4 inch and 1 inch is supported at not more than 8 foot intervals. The 6 foot spacing applies to 1/2 inch steel pipe, and 10 or 12 feet apply to larger-diameter piping; using too wide a spacing lets the line sag and stresses the joints.IFGC §415 (support table)

Natural gas and propane are odorized so that a leak is detectable in air at what concentration?

• a.At the lower flammable limit itself
• b.Only above the upper flammable limit
• c.At one-fifth (1/5) of the lower flammable limit✓
• d.Odorization is not required for fuel gas

Fuel gas must carry an odorant strong enough to be readily detected at one-fifth of the lower flammable (explosive) limit, giving a clear warning well before the mixture can ignite. Waiting until the LEL itself, or the upper limit, would mean the gas is already at or past ignitable concentration, and odorization is in fact required for these normally odorless gases.IFGC §401.4 / NFPA 54-58

Using a natural-gas sizing table at 0.5 in w.c. drop, a section must carry 120 cfh at a 40 ft length. The table shows 1/2 in pipe = 105 cfh and 3/4 in pipe = 220 cfh at 40 ft. What is the smallest pipe that will carry the load?

• a.3/4 inch (rated 220 cfh)✓
• b.1/2 inch (rated 105 cfh)
• c.Either size will work
• d.1 inch pipe is required

The pipe must carry at least 120 cfh, and 1/2 inch is rated for only 105 cfh, which is less than the demand, so you step up to the next size, 3/4 inch at 220 cfh. Choosing 1/2 inch undersizes the line and starves the appliance, 1 inch is larger than the 3/4 inch that already covers the load, and the two sizes are not interchangeable when one is below the demand.IFGC §402.4 (sizing tables)

A reduced-pressure principle backflow assembly protecting a boiler feed is required to be:

• a.Tested a single time at installation and then never again
• b.Removed and replaced with a new assembly every year as routine
• c.Tested only if someone later suspects an actual cross-connection
• d.Tested at installation and at least yearly by a certified tester✓

Testable backflow assemblies must be tested when installed and at least once a year (and after any repair) by a certified tester, with the results recorded, because internal check springs and relief valves wear and can fail silently. The device is not replaced wholesale each year, one initial test is not enough, and waiting until a problem is suspected defeats the purpose of scheduled verification.IPC §312.10 / §608.17

Two lengths of hubless (no-hub) cast-iron soil pipe are joined with:

• a.A solvent-cemented bell-and-spigot socket joint
• b.A shielded coupling with a gasket and stainless clamps✓
• c.A tapered threaded coupling made up with pipe dope
• d.A wax sealing ring compressed between the two ends

Hubless cast-iron pipe is joined with a shielded coupling: a neoprene gasket held by a stainless-steel shield and clamp bands, torqued to specification. Solvent cement is for plastic pipe, cast-iron soil pipe is not threaded at the field joint, and a wax ring seals a water closet to its flange, not a pipe-to-pipe joint.ASTM C1277 / CISPI 310

Nonpotable reclaimed (recycled) water distribution piping must be identified how, to prevent a cross-connection with the potable supply?

• a.Left unmarked, since it runs on a completely separate pressure zone
• b.Colored purple and marked nonpotable, with no tie to the potable system✓
• c.Colored the same blue as the potable cold-water distribution piping
• d.Identified only by a wrap of green tape located at the meter

Reclaimed-water piping is colored purple and marked as nonpotable so no one mistakes it for drinking water and cross-connects it to the potable system, which must stay physically separate. Leaving it unmarked, coloring it blue like the cold-water line, or taping only the meter would all invite a dangerous cross-connection.IPC §1301 / UPC §1602

A 2 in horizontal fixture branch is installed at the code-minimum slope for its size over a developed length of 24 ft. What is the total fall?

• a.3 in
• b.1-1/2 in
• c.12 in
• d.6 in✓

Drainage pipe 2-1/2 in and smaller requires a minimum slope of 1/4 in per ft, so 24 ft x 1/4 in = 6 in of fall (IPC Table 704.1; UPC agrees for this size). 3 in uses 1/8 in per ft (the rate for 3 in and larger), 12 in uses 1/2 in per ft, and 1-1/2 in uses 1/16 in per ft.

A 4 in building drain runs 120 ft at the IPC code-minimum slope for its size. What is the total fall?

• a.7-1/2 in
• b.30 in
• c.15 in✓
• d.60 in

Pipe 3 in and larger may slope at a minimum of 1/8 in per ft, so 120 ft x 1/8 in = 15 in (IPC Table 704.1). 30 in comes from 1/4 in per ft, 7-1/2 in from 1/16 in per ft, and 60 in from 1/2 in per ft.

A 3 in branch runs 40 ft at 1/4 in per ft. The upstream invert is at elevation 100.00 ft. What is the downstream invert elevation?

• a.99.58 ft
• b.99.90 ft
• c.98.33 ft
• d.99.17 ft✓

Fall = 40 ft x 1/4 in = 10 in = 0.833 ft, so 100.00 - 0.833 = 99.17 ft. 99.90 ft treats the fall as inches of elevation, 98.33 ft doubles the fall, and 99.58 ft halves it (using 1/8 in per ft).

A 6 in horizontal drain runs 88 ft at the IPC code-minimum slope for its size. What is the total fall?

• a.44 in
• b.22 in
• c.11 in✓
• d.5-1/2 in

Pipe 3 in through 6 in may slope at a minimum of 1/8 in per ft, so 88 ft x 1/8 in = 11 in. 22 in uses 1/4 in per ft, 44 in uses 1/2 in per ft, and 5-1/2 in uses 1/16 in per ft.

An 8 in building drain is sloped at 1/16 in per ft over a 160 ft run. What is the fall, and is the slope permitted?

• a.10 in, permitted for 8 in and larger where approved✓
• b.5 in, permitted
• c.20 in of fall, and this slope is not permitted on any size of drainage pipe
• d.40 in, not permitted

160 ft x 1/16 in = 10 in, and a slope as flat as 1/16 in per ft may be approved for pipe 8 in and larger where the velocity is adequate (IPC Table 704.1). 20 in and 40 in apply the 1/8 in and 1/4 in rates, and 5 in halves the correct fall.

A 3 in branch must gain exactly 6 in of fall between two points at the IPC minimum slope for 3 in pipe. What is the longest run that produces that fall?

• a.24 ft
• b.96 ft
• c.36 ft
• d.48 ft✓

At 1/8 in per ft, run = 6 in / (1/8 in per ft) = 48 ft. 24 ft uses 1/4 in per ft, 96 ft uses 1/16 in per ft, and 36 ft matches no code slope for this fall.

A branch serves one water closet at 4 DFU, two lavatories at 1 DFU each, and one shower at 2 DFU. What is the total drainage fixture unit load?

• a.6 DFU
• b.7 DFU
• c.8 DFU✓
• d.9 DFU

The loads add directly: 4 + 1 + 1 + 2 = 8 DFU. 7 drops a lavatory, 6 drops the shower, and 9 counts an extra fixture unit not in the list.

A horizontal branch serves three floor drains at 2 DFU each and one mop-basin sink at 3 DFU. What is the total drainage fixture unit load?

• a.6 DFU
• b.11 DFU
• c.7 DFU
• d.9 DFU✓

The loads add directly: 2 + 2 + 2 + 3 = 9 DFU. 7 uses only two floor drains, 6 drops the mop sink, and 11 adds a unit that is not listed.

A vertical storm conductor is rated for 10,000 sq ft of roof area at a 3 in/hr rainfall rate. At a local design rainfall rate of 5 in/hr, how much roof area may it actually serve?

• a.16,667 sq ft
• b.3,000 sq ft
• c.10,000 sq ft
• d.6,000 sq ft✓

Allowable roof area scales inversely with rainfall rate: 10,000 x (3/5) = 6,000 sq ft (IPC 1106 rainfall adjustment). Multiplying by 5/3 gives 16,667 sq ft, which overstates capacity; 10,000 ignores the heavier storm; 3,000 has no basis.

A 6 in horizontal storm drain runs 100 ft at 1/8 in per ft. What is the total fall?

• a.12-1/2 in✓
• b.25 in
• c.50 in
• d.6-1/4 in

100 ft x 1/8 in = 12-1/2 in of fall; horizontal storm drains follow the same slope minimums as sanitary drains (IPC 1106 / 704.1). 25 in uses 1/4 in per ft, 50 in uses 1/2 in per ft, and 6-1/4 in uses 1/16 in per ft.

A 3 in trap arm serves a floor-set fixture. What is the greatest fall the trap arm may have between the trap weir and the vent connection?

• a.3 in✓
• b.4 in
• c.1 in
• d.2 in

A trap arm may not fall more than one pipe diameter between the weir and the vent, so a 3 in arm may drop a maximum of 3 in (IPC 909.2; UPC agrees). A greater fall floods the crown of the arm and self-siphons the trap.

A trap is built to hold a liquid seal of 5 in. How is that trap classified?

• a.A running trap
• b.A prohibited S-trap
• c.A standard P-trap
• d.A deep seal trap✓

A standard fixture trap holds a seal of 2 in to 4 in; a seal deeper than 4 in makes it a deep seal trap, permitted only in specific approved applications (IPC 1002.4). An S-trap is a prohibited configuration and a running trap is a different device.

Under the Uniform Plumbing Code, what is the maximum developed length permitted between the trap weir and the vent for a 2 in trap arm?

• a.3-1/2 ft
• b.8 ft
• c.6 ft
• d.5 ft✓

UPC Table 1002.2 allows 5 ft for a 2 in trap arm. Code divergence: the IPC (Table 909.1) permits 8 ft for a 2 in arm, so the adopted code must be named. 3-1/2 ft is the UPC limit for a 1-1/2 in arm and 6 ft is the UPC limit for a 3 in arm.

Under the International Plumbing Code, what is the maximum developed length permitted between the trap weir and the vent for a 1-1/4 in trap arm?

• a.5 ft✓
• b.2-1/2 ft
• c.6 ft
• d.3-1/2 ft

IPC Table 909.1 permits 5 ft for a 1-1/4 in trap arm. Code divergence: the UPC (Table 1002.2) allows only 2-1/2 ft for a 1-1/4 in arm, so name the adopted code. 6 ft is the IPC limit for a 1-1/2 in arm.

A fixture drain is 4 in in diameter. What is the smallest vent that may serve it?

• a.2 in✓
• b.1-1/4 in
• c.4 in
• d.1-1/2 in

A vent must be at least one-half the diameter of the drain it serves but never smaller than 1-1/4 in. Half of 4 in is 2 in, which is above the 1-1/4 in floor, so 2 in controls. 4 in is larger than required and 1-1/4 in and 1-1/2 in are below the half-diameter here.

A 1-1/2 in fixture drain serves a lavatory. What is the smallest vent that may serve it?

• a.1-1/4 in✓
• b.3/4 in
• c.1-1/2 in
• d.1 in

Half of 1-1/2 in is 3/4 in, but a vent may never be smaller than 1-1/4 in, so the 1-1/4 in floor controls. 3/4 in and 1 in violate that minimum, and 1-1/2 in is larger than the smallest permitted size.

In a climate subject to frost closure, a vent extension through the roof must be increased to what minimum diameter?

• a.3 in✓
• b.4 in
• c.2 in
• d.1-1/2 in

Where frost closure is a concern, the vent through the roof must be at least 3 in in diameter, with the increase made not less than 1 ft inside the thermal envelope (IPC 903.1). 1-1/2 in and 2 in are too small to resist frost buildup and 4 in exceeds the minimum.

A vent terminal is 5 ft horizontally from an openable window and cannot be moved farther away. Which vertical arrangement satisfies the code?

• a.level with the top of the window
• b.3 ft above the top of the window✓
• c.2 ft above the top of the window
• d.1 ft above the top of the window

A vent terminal must be at least 10 ft horizontally from an openable window or air intake, or else extend at least 3 ft above the top of the opening (IPC 904.5 / UPC 906.2). At only 5 ft away, the 3 ft rise is what makes it compliant; the shorter rises do not.

A dry vent leaves a fixture and offsets horizontally. At what minimum elevation must the horizontal portion connect so it cannot be flooded by a stoppage?

• a.At least 6 in above the flood level rim of the fixture✓
• b.At least 12 in below the flood level rim of the fixture being vented
• c.At the trap weir
• d.Below the flood level rim

A dry vent must rise vertically to at least 6 in above the flood level rim of the fixture served before it may offset horizontally (IPC 905.4), so a downstream stoppage cannot fill the vent with waste. Connecting at the weir or below the rim would let the vent flood.

What is a yoke vent?

• a.A vent serving two fixtures whose drains both connect to the stack at the very same level
• b.A vent terminal passing through the roof
• c.A vertical vent connecting a drainage stack to its vent stack to relieve pressure✓
• d.A vent for an island sink with no adjacent wall

A yoke (relief) vent is a vertical connection between a drainage stack and its vent stack, taken off below a branch interval, used to relieve pressure buildup on tall stacks. The island fixture arrangement is a loop vent and a shared vent at the same level is a common vent.

The portion of a soil or waste stack that extends above the highest horizontal branch connected to the stack is called the:

• a.vent stack
• b.stack vent✓
• c.relief vent
• d.yoke vent

A stack vent is the dry extension of a soil or waste stack above the highest branch. A vent stack is a separate vertical vent installed to provide air circulation to the drainage system; a relief and a yoke vent connect the two systems.

Which fitting is acceptable at the base of a stack where the vertical stack turns into the horizontal building drain?

• a.A sanitary tee
• b.A long-sweep quarter bend, or two 1/8 bends✓
• c.A short quarter bend
• d.A vent tee

The base of a stack sees the highest flow velocity and must turn with a long-turn pattern such as a long-sweep quarter bend or two 1/8 bends. A short quarter bend turns too abruptly, a sanitary tee is only for horizontal-to-vertical, and a vent tee is a dry-vent fitting.

To avoid a prohibited crown vent, a vent connection to a trap arm must be located at least how far downstream of the trap weir?

• a.1 pipe diameter
• b.2 pipe diameters✓
• c.4 pipe diameters
• d.one-half pipe diameter

A vent connected within 2 pipe diameters of the trap weir is a crown vent, which clogs and fails, so the vent must be at least 2 pipe diameters downstream of the weir (IPC 909.2). The shorter distances place the vent in the crown of the trap.

Under the International Plumbing Code, a wet vent may serve fixtures located within how many bathroom groups?

• a.the fixtures within a single bathroom group only
• b.not more than 2 bathroom groups✓
• c.an unlimited number
• d.4 bathroom groups

IPC 912 allows a wet vent to serve any combination of fixtures within not more than two bathroom groups on the same floor. Limiting it to one group is stricter than the code, and allowing four or unlimited groups exceeds what a wet vent can safely serve.

A building is vented largely with air admittance valves. What does the code still require of the overall system?

• a.At least one vent open to the outside air; an AAV cannot be the only vent✓
• b.At least two roof vents
• c.One vent through the roof per fixture
• d.No open vent at all, provided an air admittance valve is fitted at every fixture

Every building drainage system must have at least one vent pipe extended to the open air (IPC 903.1). Air admittance valves admit air only and cannot relieve positive pressure, so they may supplement but never wholly replace an open vent.

Under the IPC, a vent stack is required for every drainage stack that has how many branch intervals?

• a.3 or more
• b.10 or more branch intervals in the stack
• c.5 or more branch intervals✓
• d.2 or more

IPC 903.4 requires a vent stack for any drainage stack with five or more branch intervals, because a tall stack develops pressure swings that a stack vent alone cannot relieve. Fewer than five intervals do not trigger the requirement.

In DWV terminology, a branch interval is:

• a.a 4 ft section of vent piping
• b.any fixture branch on a horizontal line
• c.a length of soil or waste stack at least 8 ft high, roughly corresponding to a story✓
• d.the distance between two cleanouts

A branch interval is a vertical length of stack, generally at least 8 ft, within which the horizontal branches from one story connect (IPC definitions). It is a measure of stack height by story, not a horizontal branch, a cleanout spacing, or a vent length.

Which fixtures are permitted to discharge through a backwater valve on the building drainage system?

• a.Only water closets
• b.All fixtures in the building, so that every fixture on every floor discharges through the one backwater valve on the sewer
• c.Only fixtures below the level of the upstream sewer or manhole; fixtures above it must not discharge through it✓
• d.Storm drainage only

Only fixtures below the elevation of the next upstream manhole or the crown of the sewer are routed through a backwater valve; fixtures above that level must not discharge through it so that normal flow is not needlessly restricted (IPC 715.1). Sanitary fixtures, not storm, are the subject.

A sewage pump or ejector discharge line must be equipped with:

• a.An air gap to the sewer
• b.A running trap installed on the pump discharge line ahead of the connection
• c.A check valve and a full-open shutoff valve on the discharge✓
• d.No valves

The discharge of a sewage pump or ejector requires a check valve to stop backflow into the pit and an accessible full-open shutoff valve so the pump can be isolated for service (IPC 712.3.4). A trap or an air gap on a pressurized sewage discharge is not appropriate.

A sewage ejector receives the discharge of a water closet. What is the minimum size of its discharge pipe?

• a.1-1/4 in
• b.3 in
• c.1-1/2 in
• d.2 in✓

A sewage ejector or pump receiving water-closet discharge must have a discharge pipe of at least 2 in so it can pass solids (IPC 712.3.2). 1-1/4 in and 1-1/2 in are undersized for sewage, and 3 in is larger than the minimum required.

Which three factors together size a horizontal storm drain?

• a.The pipe material and the number of stories the leader serves
• b.Rainfall rate, roof area drained, and pipe slope✓
• c.Fixture units only
• d.Wind speed only

A horizontal storm drain is sized from the design rainfall rate, the roof (drainage) area it serves, and the slope at which the pipe is run (IPC 1106). Drainage fixture units and pipe material do not set storm capacity, and wind speed is not a sizing input.

A floor drain connected to the sanitary drainage system must be provided with:

• a.A vent but no trap
• b.No trap
• c.A backwater valve installed in place of a trap to keep sewer gas from rising into the room
• d.A trap, plus trap-seal protection where the seal is subject to evaporation✓

A floor drain must be trapped like any other fixture, and where its seal can evaporate it also needs trap-seal protection such as a trap primer (IPC 1002.4 / 1002.1). A backwater valve does not replace the trap, and an untrapped drain admits sewer gas.

An individual air admittance valve serving a fixture must be located at least how far above the horizontal branch drain it vents?

• a.At least 4 in above the horizontal branch drain✓
• b.At the floor level
• c.Level with the flood rim
• d.Below the trap weir

An individual or branch-type air admittance valve must be installed a minimum of 4 in above the horizontal branch drain it serves (IPC 918.4) so that a surge of waste cannot reach and foul the valve. Locating it at the floor or below the weir defeats that protection.

An air admittance valve serving a branch must be located at least how far above the highest flood level rim of the fixtures served?

• a.24 in above the rim
• b.Below the rim
• c.At least 6 in above the highest flood level rim of the fixtures served✓
• d.Set exactly level with the highest flood level rim of the fixtures it serves

A branch-serving AAV must be at least 6 in above the highest flood level rim of the connected fixtures (IPC 918.3), so a backup cannot submerge the valve. Level with or below the rim allows flooding, and 24 in is more than the code minimum.

An offset in a drainage stack that turns 45 degrees or less from vertical is sized and treated as:

• a.Exempt from sizing
• b.A vertical stack✓
• c.A vent
• d.A horizontal drain

An offset of 45 degrees or less from vertical is sized as a straight vertical stack because flow behaves essentially as it does in the vertical run (IPC 711.1). An offset more than 45 degrees from vertical is the one sized as a horizontal drain.

An offset in a drainage stack that turns more than 45 degrees from vertical is sized and treated as:

• a.A vertical stack
• b.A horizontal drain✓
• c.Exempt from sizing
• d.A vent

An offset greater than 45 degrees from vertical acts like a horizontal branch and is sized as a horizontal drain, with the required slope and fitting rules (IPC 711.2). An offset of 45 degrees or less from vertical is the one sized as a stack.

Which statement about the size of a fixture trap is correct?

• a.A trap must always be at least 3 in
• b.Trap size is unrelated to the drain
• c.A trap must always be one nominal size larger than the fixture drain it discharges into
• d.A trap may not be larger than the fixture drain or trap arm it discharges into✓

A trap must not be larger than the fixture drain (trap arm) it discharges into; an oversized trap slows flow and self-siphons (IPC 1002.3). It need not be larger than the drain, and 3 in is not a universal minimum for every fixture trap.

What is the minimum trap size for a kitchen sink?

• a.3 in
• b.2 in
• c.1-1/2 in✓
• d.1-1/4 in

A kitchen sink requires a minimum 1-1/2 in trap and trap arm (IPC Table 709.1 / trap sizing). 1-1/4 in is the minimum for a lavatory, while 2 in and 3 in are larger than a sink requires.

What is the minimum trap size for a lavatory?

• a.1 in
• b.2 in
• c.1-1/4 in✓
• d.1-1/2 in

A lavatory requires a minimum 1-1/4 in trap. 1 in is below any code trap size, and 1-1/2 in and 2 in are larger than a lavatory requires (1-1/2 in is the sink minimum).

What is the minimum size for a floor drain and its trap?

• a.2 in✓
• b.1-1/2 in
• c.3 in
• d.4 in

A floor drain requires a minimum 2 in drain and trap so it can clear the volume it is meant to receive (IPC 412 / 709). 1-1/2 in is undersized for a floor drain, and 3 in and 4 in exceed the minimum.

A vertical storm conductor (leader) is sized primarily by:

• a.The roof area it drains and the design rainfall rate✓
• b.The number of drainage fixture units connected upstream of the leader
• c.The building height only
• d.The number of plumbing fixtures

A vertical rainwater conductor is sized from the roof area it serves at the local design rainfall rate (IPC Table 1106.2). Drainage fixture units size sanitary piping, not storm leaders, and building height and fixture count are not the sizing basis.

Condensate from a cooling coil (air-conditioning) must discharge:

• a.By a direct connection into the trap arm of the nearest plumbing fixture
• b.Indirectly to an approved receptor or as the code otherwise directs✓
• c.Into a vent pipe
• d.Onto the roof in all cases

Air-conditioning condensate is clear-water waste and must discharge indirectly to an approved location such as a floor drain, floor sink, or other receptor (IPC 314). It may not connect directly to a fixture or a vent.

What is the minimum size of the condensate drain for a residential cooling coil?

• a.1/2 in
• b.1-1/4 in
• c.1 in
• d.3/4 in✓

The condensate drain from a cooling coil must be at least 3/4 in for typical residential units (IPC Table 314.2.1). 1/2 in is undersized, and 1 in or larger is required only for higher-tonnage equipment.

Where a condensate overflow could damage the building, what must be provided in addition to the primary condensate drain?

• a.A backwater valve
• b.A single primary condensate line increased two pipe sizes so that it cannot clog and overflow
• c.Nothing additional
• d.An auxiliary/secondary drain pan with its own drain, or a water-level shutoff device✓

Where a clogged primary condensate drain could cause damage, the code requires a secondary drain, an auxiliary drain pan with a separate drain line, or a water-level detection shutoff (IPC 314.2.3). Enlarging the primary line alone does not provide the required backup.

Static pressure at the meter is 72 psi and the highest fixture is 45 ft above the meter. Ignoring friction and meter loss, how much pressure remains at that fixture's elevation?

• a.46.5 psi
• b.38.5 psi
• c.52.5 psi✓
• d.58.8 psi

Elevation loss is 0.433 psi per foot of rise, so 45 ft x 0.433 = 19.5 psi, and 72 - 19.5 = 52.5 psi. Using a smaller factor gives 58.8 psi; the other values misapply the head-to-pressure relationship.

How many feet of vertical head are equivalent to 35 psi of water pressure?

• a.15.2 ft
• b.35 ft
• c.80.9 ft✓
• d.70 ft

One psi equals 2.31 ft of head, so 35 x 2.31 = 80.9 ft. 15.2 ft divides by 2.31 instead of multiplying, 35 ft ignores the conversion, and 70 ft uses a factor of 2.0.

A storage tank's water surface is 90 ft above an outlet. Ignoring friction, what static pressure does that elevation produce at the outlet?

• a.39 psi✓
• b.208 psi
• c.90 psi
• d.19.5 psi

Pressure equals head times 0.433 psi per foot, so 90 x 0.433 = 39 psi. 208 psi multiplies by 2.31 (the inverse factor), 90 psi treats feet as psi, and 19.5 psi halves the correct value.

A potable supply outlet has an effective opening of 1/2 in and discharges over a receptor. What is the minimum required air gap?

• a.1 in✓
• b.1/2 in
• c.3/4 in
• d.1-1/2 in

The air gap must be at least twice the effective opening, so 2 x 1/2 in = 1 in, which also meets the 1 in absolute minimum (IPC 608.15.1). 1/2 in and 3/4 in are below the calculated and minimum values, and 1-1/2 in exceeds what this opening requires.

A potable supply outlet has an effective opening of 3/4 in. What is the minimum required air gap above the flood level rim?

• a.2 in
• b.3/4 in
• c.1-1/2 in✓
• d.1 in

Twice the effective opening is 2 x 3/4 in = 1-1/2 in, which is above the 1 in absolute minimum, so 1-1/2 in governs (IPC 608.15.1). 3/4 in and 1 in are too small and 2 in is more than required.

Static pressure is 70 psi, meter loss is 8 psi, the highest fixture is 30 ft above the meter, and 15 psi residual is required there. How much pressure remains for friction loss in the piping?

• a.40.0 psi
• b.21.0 psi
• c.34.0 psi✓
• d.47.0 psi

Elevation loss is 30 x 0.433 = 13 psi, so 70 - 8 - 13 - 15 = 34 psi available for friction. 47.0 psi omits the elevation loss, 40.0 psi understates it, and 21.0 psi subtracts an extra loss.

A sizing problem leaves 26 psi available for friction. The measured developed length to the most remote fixture is 160 ft and fittings are estimated to add 50 percent. What is the allowable friction loss per 100 ft of pipe?

• a.26 psi per 100 ft
• b.6.5 psi per 100 ft
• c.16.3 psi per 100 ft
• d.10.8 psi per 100 ft✓

Total equivalent length is 160 x 1.5 = 240 ft, so 26 / 240 x 100 = 10.8 psi per 100 ft. 16.3 uses only the measured 160 ft, 6.5 overstates the equivalent length, and 26 skips the division by length.

A dwelling has one flush-tank water closet (2.5 WSFU), one bathtub with shower (2.0 WSFU), one lavatory (1.0 WSFU), one kitchen sink (1.5 WSFU), and one clothes washer (4.0 WSFU). What is the total water supply fixture unit load?

• a.12.5 WSFU
• b.10.0 WSFU
• c.11.0 WSFU✓
• d.9.0 WSFU

Adding the listed values: 2.5 + 2.0 + 1.0 + 1.5 + 4.0 = 11.0 WSFU. 9.0 and 10.0 drop a fixture, and 12.5 adds load not in the list. The total is then read against the sizing table.

Using velocity (fps) = 0.408 x flow (gpm) / inside diameter squared (in), what is the velocity of 8 gpm in 1/2 in Type L copper with an inside diameter of 0.545 in?

• a.6.0 fps
• b.5.5 fps
• c.8.0 fps
• d.11.0 fps✓

0.408 x 8 = 3.264, and 0.545 squared is 0.297, so 3.264 / 0.297 = 11.0 fps, well above the practical 8 fps cold-water limit, which shows 1/2 in is too small for 8 gpm. The lower answers divide by the diameter rather than its square.

The highest fixture is 35 ft above the meter and needs 15 psi residual, meter loss is 6 psi, and friction loss is 14 psi. What minimum static pressure is needed at the meter?

• a.35.0 psi
• b.50.2 psi✓
• c.44.0 psi
• d.29.0 psi

Add every loss to the residual: 35 x 0.433 = 15.2 psi elevation, plus 6 meter, plus 14 friction, plus 15 residual = 50.2 psi. 35.0 omits the elevation loss and 44.0 understates it.

An 80 ft straight run of CPVC will see a 80 degree F temperature change. Using a thermal-expansion coefficient of 0.000034 in per in per degree F, about how much will it move?

• a.1.3 in
• b.3.9 in
• c.0.9 in
• d.2.6 in✓

Convert to inches: 80 ft = 960 in, and 960 x 0.000034 x 80 = 2.6 in, so an offset or expansion loop is needed. 1.3 in halves the movement and 3.9 in overstates the temperature change.

Under IPC Table 604.3, what minimum flow pressure is required at a flushometer-valve water closet?

• a.8 psi
• b.25 psi✓
• c.35 psi
• d.15 psi

A flushometer-valve water closet requires about 25 psi minimum flow pressure to operate the valve (IPC Table 604.3), far more than a tank fixture. 8 psi is the lavatory requirement, and 15 psi and 35 psi are not the tabulated value for this fixture.

Under IPC Table 604.3, what minimum flow pressure is required at a lavatory faucet?

• a.15 psi
• b.8 psi✓
• c.20 psi
• d.4 psi

A lavatory faucet requires a minimum flow pressure of about 8 psi (IPC Table 604.3). 4 psi is below the tabulated value, and 15 psi and 20 psi are higher than a lavatory needs (closer to flushometer requirements).

A chemical feed connection to the potable supply is a high-hazard (health) cross-connection subject to back-pressure under continuous pressure. Which device is required?

• a.A reduced pressure principle assembly✓
• b.A double check valve assembly
• c.A pressure vacuum breaker
• d.An atmospheric vacuum breaker on the branch

A high-hazard connection with back-pressure under continuous pressure requires a reduced pressure principle assembly (IPC 608.13.2). A double check is only for low hazard, and vacuum breakers protect against back-siphonage, not back-pressure.

An atmospheric vacuum breaker (AVB) may NOT have which of the following?

• a.A fixture or outlet located below it on the same branch that it protects against back-siphonage
• b.Copper piping upstream
• c.A hose thread outlet
• d.Any valve downstream of it, and it may not be under continuous pressure for more than 12 hours✓

An AVB relies on atmospheric venting, so no shutoff valve may be located downstream of it and it may not be under continuous pressure for more than 12 hours (IPC 608.13.6). Upstream piping material and a downstream fixture do not disqualify it.

How does a pressure vacuum breaker (PVB) differ from an atmospheric vacuum breaker?

• a.It needs no minimum installation height
• b.It protects against both back-pressure and back-siphonage, so it may be used on any cross-connection regardless of the hazard level involved
• c.It is for back-pressure only
• d.It may be installed under continuous pressure and has test cocks and a spring-loaded check, but protects only against back-siphonage✓

A PVB has a spring-loaded air inlet and check plus test cocks, so it may stay under continuous pressure and can be tested, unlike an AVB. It still protects only against back-siphonage, not back-pressure, and must be at least 12 in above the highest downstream outlet.

Which material is NOT approved for hot-water distribution piping?

• a.PEX
• b.CPVC
• c.Type L copper
• d.PVC✓

PVC is rated for cold-water and DWV service only and will soften and fail on hot water; CPVC is the chlorinated version made for hot water. Type L copper and PEX are both approved for hot-water distribution.

Before a new potable water line is placed in service, it must be:

• a.Left as installed
• b.Filled with hot water
• c.Pressure tested with air only, then placed directly in service
• d.Disinfected (chlorinated) and flushed✓

New potable water piping must be disinfected with a chlorine solution and then flushed before use to remove contamination introduced during installation (IPC 610.1). A pressure test alone does not sanitize the pipe.

What must be provided on the water service near where it enters the building?

• a.Only a pressure-reducing valve, with no separate shutoff on the service
• b.Only a check valve
• c.No valve at all
• d.An accessible main shutoff valve on the water service✓

A full-open, accessible main shutoff valve is required on the water service so the whole building supply can be isolated (IPC 606.1). A check valve or a pressure-reducing valve serves a different purpose and does not satisfy the main-shutoff requirement.

What does the code require at each individual fixture supply?

• a.A check valve at each fixture
• b.A single shutoff valve at the main, which serves all of the fixtures at once
• c.An accessible shutoff (stop) valve on each fixture supply✓
• d.No shutoffs at fixtures

Each fixture supply must have an accessible individual stop valve so the fixture can be serviced without shutting down the whole building (IPC 606.2 lists where stops are required). A single main shutoff does not meet the individual-fixture requirement.

Why are listed mechanical water-hammer arrestors preferred over plain air chambers?

• a.Air chambers are illegal
• b.There is no difference
• c.Air chambers are cheaper
• d.Plain air chambers waterlog and lose their air cushion over time, while listed arrestors keep their charge✓

A capped-pipe air chamber gradually absorbs its air into the water and waterlogs, losing its cushion, whereas a listed mechanical arrestor keeps a sealed air or gas charge. That reliability is why arrestors are specified for quick-closing valves.

In water-service sizing, how is the pressure lost through the water meter handled?

• a.Ignored
• b.Relevant only for wells
• c.Subtracted from the available pressure before sizing the piping✓
• d.Added to the available pressure, since the meter is said to boost downstream flow

Meter pressure loss at design flow is one of the deductions taken from the static supply pressure, along with elevation, residual, and backflow-device losses, before the remainder is left for pipe friction. Ignoring it oversizes the friction budget and undersizes the pipe.

For water-distribution sizing, the developed length is measured:

• a.Along the actual pipe run to the most remote fixture✓
• b.To the nearest fixture
• c.As only the vertical rise
• d.As the straight-line (as-the-crow-flies) distance to the most remote fixture

Developed length is measured along the centerline of the pipe, following every offset, to the most hydraulically remote fixture, since that path governs friction loss. A straight-line or nearest-fixture measurement understates the run.

What is the generally accepted maximum design velocity for a cold-water distribution line?

• a.5 fps
• b.12 fps
• c.8 fps✓
• d.15 fps

Cold-water lines are commonly designed to a maximum of about 8 fps to limit noise and erosion; hot-water lines are held lower, near 5 fps. 12 fps and 15 fps are well above accepted practice and cause velocity noise and pipe wear.

A common method of disinfecting new potable piping uses a chlorine concentration and contact time of about:

• a.5 ppm for 1 hour
• b.No minimum concentration is specified; a simple flush with clean water is enough
• c.50 ppm held about 24 hours (or 200 ppm for about 3 hours)✓
• d.500 ppm for 10 minutes

A typical disinfection procedure charges the system to at least 50 ppm chlorine for about 24 hours, or a stronger 200 ppm for about 3 hours, then flushes and confirms an acceptable residual (IPC 610.1). A brief 5 ppm dose is too weak and short.

What is the minimum supply pipe size for a hose bibb (sillcock)?

• a.1 in
• b.3/8 in
• c.1/4 in
• d.1/2 in✓

A hose bibb requires a minimum 1/2 in supply (IPC Table 604.5). 1/4 in and 3/8 in are undersized, and 1 in is far larger than a single sillcock needs.

A water-distribution system is tested with water at not less than its working pressure. For how long must the pressure hold with no drop?

• a.15 minutes✓
• b.1 hour
• c.5 minutes
• d.10 minutes

The water-supply test holds at not less than the working pressure for at least 15 minutes with no loss of pressure (IPC 312.5). Any drop indicates a leak; 5 or 10 minutes is short of the required duration.

A lawn irrigation system injects fertilizer or chemicals into the water. What backflow protection does this high-hazard connection require?

• a.A double check valve assembly on the irrigation branch
• b.A reduced pressure principle assembly✓
• c.An atmospheric vacuum breaker
• d.A pressure vacuum breaker

Chemical injection makes irrigation a high-hazard (health) connection, and where it is under continuous pressure or subject to back-pressure it requires a reduced pressure principle assembly (IPC 608.13.2). A vacuum breaker or double check does not protect a high-hazard, back-pressure connection.

Which materials are commonly used for an underground water service?

• a.CPVC only
• b.Type M copper only
• c.Type K copper or PE plastic✓
• d.Galvanized steel pipe only, because it resists corrosion in soil

Underground water services are commonly Type K copper (the heaviest wall) or polyethylene (PE) plastic, both suited to burial (IPC 605 / UPC 604). Type M is generally restricted to above-ground use, and galvanized steel corrodes in soil.

Which provides the most positive, reliable backflow protection for a cross-connection?

• a.An atmospheric vacuum breaker
• b.A pressure vacuum breaker
• c.An air gap (a physical separation)✓
• d.A double check valve assembly

An air gap is a physical vertical separation of at least twice the supply-opening diameter and cannot fail mechanically, so it is the most reliable backflow protection (IPC 608.15.1). Mechanical assemblies rely on checks and springs that can wear.

Where must a lavatory faucet spout be located relative to the flood level rim of the basin?

• a.At the flood level rim
• b.Below the flood level rim
• c.Above the flood level rim to maintain an air gap✓
• d.Submerged in the basin

The faucet spout must terminate above the flood level rim of the fixture so that if the basin fills and the supply loses pressure, contaminated water cannot be siphoned back through the spout (IPC 608.15.1). A spout at or below the rim creates a submerged-inlet cross-connection.

A flushometer valve must be provided with what backflow protection?

• a.An air gap only
• b.An integral (built-in) vacuum breaker✓
• c.A check valve only
• d.No backflow protection

A flushometer discharges below the rim of the fixture, so it must have an integral vacuum breaker downstream of the valve to prevent back-siphonage of fixture water into the supply (IPC 608.15.4). A plain check valve does not provide this protection.

A storage water heater's combination temperature and pressure relief valve is typically rated to open at about:

• a.210 degrees F / 150 psi✓
• b.180 degrees F / 75 psi
• c.250 degrees F / 300 psi
• d.140 degrees F / 50 psi

A standard residential T and P relief valve is rated to relieve at 210 degrees F and 150 psi, protecting the tank from both overheating and overpressure (IPC 504.4). The other settings do not match the listed valve ratings.

The discharge pipe from a water heater's temperature and pressure relief valve must be:

• a.Fitted with a service shutoff valve
• b.Directed upward
• c.The full size of the valve outlet, draining by gravity, with no valve in the line✓
• d.Reduced to 1/2 in copper for a neater appearance and terminated well above the floor

The T and P discharge pipe must be full size of the valve outlet, drain by gravity, contain no valves, and terminate 6 to 24 in above an approved location with no threads on the end (IPC 504.6). Reducing it, valving it, or running it upward is prohibited.

A storage water heater must be equipped with:

• a.No drain valve
• b.A check valve on the outlet
• c.A drain valve at its lowest point✓
• d.Only a vacuum relief valve

A storage water heater must have a drain valve at its lowest point so the tank can be flushed and drained for service (IPC 504.3). A vacuum relief valve is required only on bottom-fed tanks and does not replace the drain.

A 100,000 Btu/h water heater draws combustion air from outdoors through two horizontal ducts. Using 1 square inch per 2,000 Btu/h for horizontal ducts, what free area must each opening have?

• a.100 square inches
• b.25 square inches
• c.50 square inches✓
• d.12-1/2 square inches

100,000 / 2,000 = 50 square inches for each of the two openings. The vertical-duct method uses 1 square inch per 4,000 Btu/h; using that gives 25, which understates the horizontal-duct requirement.

Using the single-opening (one permanent opening) method that communicates directly with the outdoors at 1 square inch per 1,000 Btu/h, what free area is required for a 120,000 Btu/h appliance?

• a.60 square inches
• b.30 square inches
• c.120 square inches✓
• d.240 square inches

120,000 / 1,000 = 120 square inches, and the single opening must also be at least the sum of the appliance connectors (minimum 100 square inches typically). 30 and 60 apply the 4,000 or 2,000 ratios used for two-opening methods.

A listed flammable-vapor-ignition-resistant (FVIR) gas water heater is installed in a residential garage. What does its listing allow?

• a.It must still be elevated 18 in in all cases
• b.It may be installed at floor level, because it resists igniting flammable vapors✓
• c.It requires no venting
• d.It is prohibited in garages

An FVIR water heater has a flame-arrestor design listed to resist igniting flammable vapors, so it may be installed at floor level in a garage where an ordinary heater would need its ignition source 18 in above the floor. It still must be vented normally.

A single-wall metal vent connector on a gas water heater must maintain what minimum clearance to combustible material?

• a.18 in
• b.6 in✓
• c.12 in
• d.1 in

A single-wall metal vent connector must be kept at least 6 in from combustibles (IFGC / NFPA 54). 1 in is unsafe, and 12 in or 18 in is more clearance than the connector requires (double-wall connectors allow less).

A water heater is set in an attic where a leak could damage the building, so a drain pan is installed. The pan itself must be at least how deep?

• a.1/2 in deep
• b.1-1/2 in deep✓
• c.12 in deep
• d.6 in deep

A water-heater drain pan must be at least 1-1/2 in deep and piped with a minimum 3/4 in indirect drain to an approved point (UPC 507.5 / IPC 504.7). 1/2 in is too shallow to hold a leak, and 6 or 12 in is deeper than required.

At a two-handle fixture fitting, which side is the hot water on as the user faces the fixture?

• a.The bottom
• b.The right
• c.Either side
• d.The left✓

By long-standing convention and code, hot water is supplied on the left and cold on the right at a fitting (IPC 607.1), so users can predict which handle delivers hot water. Reversing them is a scald hazard, and the arrangement is not optional.

What is the maximum flush volume permitted for a water closet under the model-code water-use limits?

• a.1.0 gpf
• b.1.6 gpf✓
• c.3.5 gpf
• d.1.28 gpf

The maximum is 1.6 gallons per flush (IPC 604.4 / EPAct). 1.28 gpf is a high-efficiency level below the maximum, 3.5 gpf is a pre-1994 volume no longer permitted, and 1.0 gpf is a urinal-range value.

What is the maximum flow rate for a residential lavatory faucet at 60 psi?

• a.2.2 gpm✓
• b.0.5 gpm
• c.1.5 gpm
• d.2.5 gpm

A residential lavatory faucet is limited to 2.2 gpm at 60 psi (IPC 604.4). 2.5 gpm is the showerhead limit at 80 psi, and 0.5 gpm applies to public metering/lavatory faucets, not a residential faucet.

What is the maximum flow rate for a public lavatory faucet (other than metering)?

• a.0.5 gpm✓
• b.0.25 gpm
• c.2.2 gpm
• d.2.5 gpm

A public lavatory faucet is limited to 0.5 gpm (IPC 604.4). 0.25 gallon is the per-cycle limit for a metering faucet (a volume, not a flow rate), 2.2 gpm is the residential lavatory limit, and 2.5 gpm is the showerhead limit.

How must the floors of a commercial kitchen with food-prep and wash areas be arranged for drainage?

• a.No drains are needed
• b.The floors are graded to floor drains or floor sinks✓
• c.Carpet is acceptable
• d.Provided with floor drains only in the attached restrooms, not on the cook line

Commercial kitchen floors must be sloped to floor drains or floor sinks so wash-down and spillage drain away, keeping the surface sanitary. Omitting drains or using carpet is not acceptable in a food-service wet area.

A hydromechanical (point-of-use) grease interceptor requires what on its inlet side?

• a.A food grinder discharging into it
• b.A flow-control fitting with an air (vent) intake ahead of it✓
• c.A connection downstream of a water closet
• d.No flow control

A hydromechanical grease interceptor must have a flow-control fitting with an air intake so influent is limited to the rated flow and grease can separate (IPC 1003.3.1). A disposer or water-closet waste is prohibited from a grease interceptor.

A large gravity grease interceptor for a restaurant is usually located:

• a.Outdoors, underground, with manhole access✓
• b.In the attic
• c.Inside the walk-in cooler
• d.Directly under the kitchen sink where it is easiest to reach

A large gravity grease interceptor is a buried tank located outdoors with manhole access so it can be pumped, sized for many minutes of retention. A small hydromechanical unit is the type placed under a sink; the other locations are not serviceable.

A commercial laundry with washing machines must discharge through what interceptor to protect the drainage system?

• a.A lint interceptor or trap✓
• b.No interceptor
• c.A grease interceptor sized for the washing machines
• d.An oil interceptor

Commercial laundry waste carries lint and string that clog drains, so it must pass through a lint interceptor with a removable screen (IPC 1003.6). A grease or oil interceptor targets different contaminants.

A facility that discharges sand and grit, such as a car wash, must drain through:

• a.No interceptor
• b.A lint trap
• c.A grease interceptor ahead of the connection
• d.A sand or solids interceptor✓

Sand and heavy solids must settle out in a sand/solids interceptor before the water enters the sewer (IPC 1003.7). A grease or lint device is designed for fats or fibers, not grit, and would not capture settling solids.

What is the minimum supply pipe size for a flush-tank water closet?

• a.3/8 in✓
• b.1/2 in
• c.1 in
• d.1/4 in

A flush-tank water closet requires a minimum 3/8 in supply (IPC Table 604.5), since the tank refills slowly between flushes. A flushometer water closet, by contrast, needs a 1 in supply for its high instantaneous draw.

What is the minimum supply pipe size for a bathtub?

• a.1/2 in✓
• b.3/8 in
• c.1 in
• d.3/4 in

A bathtub requires a minimum 1/2 in supply (IPC Table 604.5). 3/8 in serves a water-closet tank or lavatory, and 3/4 in or 1 in is larger than a tub requires.

What is the minimum diameter of a residential clothes-washer standpipe?

• a.1-1/2 in
• b.2 in✓
• c.1-1/4 in
• d.3 in

A clothes-washer standpipe must be a minimum of 2 in in diameter to handle the pump's high discharge rate without overflowing (IPC 802.4). 1-1/2 in and 1-1/4 in are undersized, and 3 in exceeds the minimum.

A clothes-washer standpipe trap must be located at what height above the floor?

• a.At the ceiling
• b.48 in above the floor
• c.Below the floor
• d.6 in to 18 in above the floor✓

The standpipe trap must be set between 6 in and 18 in above the floor (IPC 802.4), keeping the seal accessible and at a workable height while the standpipe rises above it. Below the floor or at the ceiling is outside the allowed range.

The floor of a shower compartment must slope to the drain at a minimum of:

• a.1/4 in per ft✓
• b.1/8 in per ft
• c.1 in per ft
• d.1/2 in per ft

A shower floor must slope to the drain at not less than 1/4 in per ft (about 2 percent) so water does not stand (UPC 408.5 / IPC 417.5.2). 1/8 in per ft is too flat and 1/2 in or 1 in per ft is steeper than required and awkward to stand on.

A model-code showerhead is limited to 2.5 gpm at 80 psi. Where several showerheads serve one shower compartment, many codes limit the flow to:

• a.1.5 gpm
• b.2.5 gpm combined for the compartment✓
• c.2.0 gpm
• d.5.0 gpm

The model-code maximum is 2.5 gpm per showerhead at 80 psi, and many adopted codes limit the combined flow of all heads serving one compartment to 2.5 gpm as well, so confirm the adopted code. Treating each head as a separate 2.5 gpm allowance can exceed the limit.

What is the minimum drain size for a commercial food-waste grinder (disposer)?

• a.2 in✓
• b.1-1/4 in
• c.1-1/2 in
• d.3 in

A commercial food-waste grinder requires a minimum 2 in drain and trap because of the volume and character of its discharge (IPC 704 / manufacturer listing). 1-1/2 in serves a residential disposer, and 1-1/4 in is far too small.

What is the minimum drain size for a residential food-waste grinder (disposer)?

• a.1-1/2 in✓
• b.3 in
• c.2 in
• d.1-1/4 in

A residential disposer discharges through the kitchen-sink drain and requires a minimum 1-1/2 in drain and trap. 1-1/4 in is the lavatory minimum and is undersized for a disposer, while 2 in is the commercial-grinder minimum.

What is the minimum trap and drain size for a bathtub?

• a.3 in
• b.1-1/4 in
• c.2 in
• d.1-1/2 in✓

A bathtub requires a minimum 1-1/2 in trap and drain (IPC Table 709.1). 1-1/4 in is the lavatory minimum and is undersized for a tub, and 2 in or 3 in exceeds what a tub requires.

An emergency eyewash or drench shower for worker safety must deliver tepid water in what temperature range?

• a.32 to 50 degrees F
• b.About 140 degrees F
• c.110 to 120 degrees F
• d.60 to 100 degrees F✓

Emergency eyewash and shower equipment must deliver tepid flushing fluid, generally 60 to 100 degrees F (ANSI/ISEA Z358.1), so a victim can tolerate a full flush without cold shock or scalding. 110 degrees and above is a scald risk and near-freezing water drives victims off the unit.

A bathtub trap and its waste-and-overflow concealed in a wall or floor must be provided with:

• a.No access, since it is concealed
• b.A wall that is cut open each time service is needed
• c.The overflow opening only
• d.An access panel or other approved access to the trap and waste✓

Concealed slip-joint connections such as a tub waste-and-overflow must remain accessible through an access panel or removable access so the joints can be serviced (IPC 405.8 / 712 access rules). Sealing them permanently behind finished construction is not permitted.

To control Legionella growth, stored hot water in a water heater is generally kept at a minimum of about:

• a.110 degrees F
• b.90 degrees F
• c.180 degrees F
• d.140 degrees F✓

Storing water at about 140 degrees F suppresses Legionella, while the water delivered to fixtures is tempered down (for example to 110 degrees F at public lavatories) with a mixing valve to prevent scalding. 90 and 110 degrees are within the range where the bacteria thrive.

A fuel-fired water heater installed in a bathroom or a bedroom must be:

• a.Any atmospheric-vented type
• b.Prohibited entirely
• c.Limited to an electric water heater only, because no gas-fired unit of any kind may ever be placed in a bedroom or bathroom
• d.A direct-vent or sealed-combustion type, or installed in a sealed enclosure with combustion air from outdoors✓

A fuel-burning water heater in a bedroom or bathroom must be a direct-vent unit or be enclosed in a sealed room that draws combustion air from outdoors, so occupants are not exposed to combustion products in a sleeping or bathing space (IFGC / IRC). An open atmospheric unit is not allowed there.

A house on natural gas (about 1,000 Btu per cubic foot) has an 80,000 Btu/h furnace, a 30,000 Btu/h water heater, and a 30,000 Btu/h range. What total flow must the piping downstream of the meter carry?

• a.56 cfh
• b.14 cfh
• c.140 cfh✓
• d.1,400 cfh

Total load is 80,000 + 30,000 + 30,000 = 140,000 Btu/h, and dividing by 1,000 Btu per cubic foot gives 140 cfh. 14 and 1,400 misplace a decimal, and 56 comes from dividing by 2,500 (a propane value).

A propane appliance load totals 125,000 Btu/h. Using about 2,500 Btu per cubic foot for propane vapor, what flow must the piping carry?

• a.50 cfh✓
• b.125 cfh
• c.31 cfh
• d.500 cfh

For propane, cfh = Btu/h / 2,500, so 125,000 / 2,500 = 50 cfh. 125 cfh uses the 1,000 Btu natural-gas value, 500 cfh divides by an incorrect small value, and 31 cfh uses about 4,000 Btu per cubic foot, which no common fuel gas has.

The most remote gas outlet measures 62 ft from the meter, and the sizing table is printed in 10 ft increments. Which length row is used?

• a.70 ft✓
• b.62 ft
• c.60 ft
• d.50 ft

When the developed length falls between rows, the next longer row is used, so 62 ft is sized from the 70 ft column. Rounding down to 60 ft (or 50 ft) allows more pressure drop than the table assumes and undersizes the pipe.

At 50 ft, a natural-gas table shows 1/2 in pipe rated for 56 cfh and 3/4 in for 115 cfh. A section must carry 60 cfh. What is the smallest pipe that works?

• a.1 in
• b.1/2 in
• c.3/8 in
• d.3/4 in✓

The pipe must carry at least 60 cfh; 1/2 in is rated for only 56 cfh, which is below the demand, so you step up to 3/4 in at 115 cfh. Choosing 1/2 in starves the appliance, and 1 in is larger than needed once 3/4 in covers the load.

What is the purpose of a sediment trap (drip leg) ahead of an appliance control valve?

• a.It regulates the gas pressure
• b.It collects moisture and debris before they reach the appliance control valve✓
• c.It acts as the shutoff valve
• d.It vents the regulator

A sediment trap is a capped drip pocket that catches moisture and scale carried in the gas so they do not foul the appliance control valve (IFGC 408.4). It does not regulate pressure, shut off gas, or vent a regulator.

What is the maximum length of a listed appliance connector serving a furnace (not a range or dryer)?

• a.3 ft✓
• b.1 ft
• c.6 ft
• d.10 ft

Most appliance connectors are limited to 3 ft (IFGC 411). Ranges and clothes dryers are the exception, permitted up to 6 ft; a furnace connector is held to the 3 ft general limit.

A listed appliance connector may:

• a.Pass through a wall if it is sleeved
• b.Be joined to a second connector to gain length
• c.Be reused from a previous appliance
• d.Not pass through walls, floors, ceilings, or partitions✓

An appliance connector may not pass through any wall, floor, ceiling, or partition, may not be concealed, and may not be joined to another connector or reused (IFGC 411). Where those conditions arise, rigid pipe must be run to a valve near the appliance.

Threaded black-steel gas pipe joints are made up with:

• a.Solvent cement
• b.An approved gas-rated thread sealant (pipe dope), or PTFE tape listed for gas✓
• c.A wax ring
• d.A rubber gasket slip coupling

Steel gas-pipe threads are sealed with a joint compound or tape listed as resistant to the gas (IFGC 403.9.2). Solvent cement is for plastic, a wax ring seals a closet, and a rubber slip coupling is a drainage fitting, none rated for gas joints.

Copper tube may be used for natural gas only when:

• a.Only when painted
• b.Never permitted for natural gas under any condition, since sulfur always attacks it
• c.Only when buried underground
• d.The gas is not corrosive (limited hydrogen sulfide content)✓

Copper is permitted for fuel gas only where the gas is not corrosive to copper, meaning the hydrogen sulfide content is below the code limit (IFGC 403.4.3), because sulfur attacks copper. It is not categorically prohibited, and burial or paint is not the deciding factor.

Where is a drip leg (drip) installed in a fuel-gas piping system?

• a.Never in residential work
• b.At low points where condensate can collect, and commonly at each appliance✓
• c.Only on outdoor piping
• d.At the highest point of the system

A drip is installed at low points where liquid can collect and typically at each appliance connection so moisture is trapped before it reaches the control (IFGC 408). Placing it at the high point would defeat the purpose, and drips are used in residential systems.

Compared with air, LP-gas (propane) vapor is:

• a.Heavier than air, so it settles at low points✓
• b.Nonflammable
• c.Lighter than air, so it rises to the ceiling
• d.The same density as air

Propane vapor is heavier than air and pools in low areas such as pits, basements, and floor level, which is why LP appliances and gas detectors account for low accumulation. Natural gas, by contrast, is lighter than air and rises.

A 250-gallon propane tank is filled to the maximum safe fill of 80 percent. How many gallons of liquid propane does it hold?

• a.250 gal
• b.125 gal
• c.200 gal✓
• d.150 gal

A propane tank is filled to a maximum of 80 percent to leave room for vapor expansion, so 250 x 0.80 = 200 gal. Filling to 250 gal (100 percent) is unsafe, and 125 or 150 gal understates the 80 percent fill.

A propane appliance with an input of 100,000 Btu/h runs continuously. Using about 91,500 Btu per gallon, roughly how long will 100 gallons last?

• a.46 hours
• b.9 hours
• c.183 hours
• d.91.5 hours✓

100 gallons holds 9,150,000 Btu, and 9,150,000 / 100,000 = 91.5 hours. Doubling the burn rate gives 46 hours, halving it gives 183 hours, and 9 hours misplaces a decimal.

What is the approximate heating value of propane vapor?

• a.About 1,000 Btu per cubic foot
• b.About 500 Btu per cubic foot
• c.About 2,500 Btu per cubic foot✓
• d.About 91,500 Btu per cubic foot

Propane vapor carries about 2,500 Btu per cubic foot, roughly two and a half times natural gas at about 1,000 Btu per cubic foot. The 91,500 figure is the energy per gallon of liquid propane, not per cubic foot of vapor.

A residence is served by a 2 psi gas system, but the appliances require about 7 in w.c. What is installed to make this work?

• a.A check valve
• b.A larger gas meter
• c.Nothing is required, because the utility service regulator already delivers the correct appliance pressure
• d.A line pressure regulator, with overpressure protection, to step the pressure down✓

An elevated-pressure (2 psi) system requires a line pressure regulator, with downstream overpressure protection, to reduce the pressure to the roughly 7 in w.c. the appliances need (IFGC 410). A larger meter or a check valve does not regulate delivery pressure.

After a gas piping system is tested and put into service, it is purged of air:

• a.Purging is not required
• b.Through an appliance burner only
• c.To the outdoors, away from ignition sources✓
• d.Into the building through a window

Piping must be purged to the outdoors or to a safe point away from any ignition source, never into an occupied space, so an air-gas mixture cannot accumulate and ignite (IFGC 406.7). Purging is required whenever a system is placed in or returned to service.

How must vertical gas piping be supported?

• a.It is never required to be supported, since the fittings alone carry the weight of the riser
• b.Every 2 ft
• c.At each floor level, and at intervals that prevent movement✓
• d.Only at the top of the riser

Vertical gas piping must be supported at each floor level (and at intervals for larger pipe) so its weight is carried and it cannot shift and stress the joints (IFGC 415). Supporting only the top, or not at all, leaves the riser unsupported.

A gas meter must be located:

• a.In a ventilated, accessible location clear of ignition sources and building openings✓
• b.Inside a sealed closet
• c.Inside a return-air plenum
• d.Below grade inside a covered pit in every case, so that the meter is protected from the weather

A gas meter is placed in a ventilated, accessible location where a leak can disperse and away from ignition sources, windows, and air intakes. A sealed closet or a return-air plenum would trap or distribute leaking gas.

What is the minimum depth of cover for underground gas piping in an area with no vehicle traffic?

• a.36 in
• b.24 in
• c.6 in
• d.12 in✓

Underground gas piping requires at least 12 in of cover in general (IFGC 404.12). 6 in leaves the pipe vulnerable to damage, and 24 or 36 in is deeper than the general minimum (deeper cover applies under driveways and roads).

What is the minimum depth of cover for underground gas piping installed beneath a private driveway?

• a.6 in
• b.36 in
• c.12 in
• d.18 in✓

Under a driveway or parking area the cover is increased to at least 18 in to protect the pipe from vehicle loads (IFGC 404.12). The 12 in general minimum is not enough under traffic, and 6 in is far too shallow.

Which of the following is prohibited in a concealed gas-piping location?

• a.A straight, unbroken length of pipe with no fittings at all
• b.A union, bushing, or right-and-left coupling✓
• c.A welded joint
• d.An elbow

Unions, bushings, swing joints, and right-and-left couplings are prohibited in concealed locations because they are the joints most likely to loosen and leak where no one can inspect them (IFGC 404.5). Welded joints and standard fittings on run pipe are permitted concealed.

On detecting a gas leak in a building, which action must you NOT take?

• a.Operating electrical switches or creating any spark or flame✓
• b.Shutting the gas off at the meter if it is safe to do so
• c.Leaving the area
• d.Calling the utility from outside the building

You must not operate electrical switches, light a flame, or do anything that could create a spark, since any of these can ignite an accumulated gas-air mixture. The correct steps are to evacuate, shut off the gas if safe, and call the utility from a safe location outside.

A DWV section is water tested. The highest joint in the section is 24 ft above the building drain, and more piping continues above this section. To what height above the building drain must the test standpipe extend?

• a.10 ft
• b.24 ft
• c.29 ft
• d.34 ft✓

The water test requires at least a 10 ft head on the highest point of the section, so the standpipe must rise 24 + 10 = 34 ft above the building drain (IPC 312.2). Stopping at 24 ft puts no head on the top joint; the 10 ft exception does not apply because piping continues above.

What is the normal sequence of plumbing inspections?

• a.Final, then rough, then groundwork
• b.Groundwork/underground, then rough-in/top-out, then final✓
• c.In any order the contractor prefers
• d.Rough, then final, then groundwork

Inspections follow the order of construction: underground/groundwork first, then rough-in (top-out) before concealment, then the final inspection when fixtures are set (IPC 107). No portion may be covered until it has been inspected and approved.

A floor plan is drawn at a scale of 1/8 in = 1 ft. A run of pipe measures 5 in on the drawing. What is its actual length?

• a.20 ft
• b.64 ft
• c.5 ft
• d.40 ft✓

At 1/8 in = 1 ft, each inch on the drawing equals 8 ft, so 5 in x 8 ft = 40 ft. Reading 5 ft ignores the scale, 20 ft multiplies by 4, and 64 ft multiplies inches the wrong way.

A floor plan is drawn at 1/4 in = 1 ft. A pipe run measures 2-1/2 in on the drawing. What is its actual length?

• a.2-1/2 ft
• b.10 ft✓
• c.5 ft
• d.20 ft

At 1/4 in = 1 ft, each inch equals 4 ft, so 2.5 in x 4 ft = 10 ft. 2-1/2 ft repeats the measured inches as feet, 5 ft multiplies by 2, and 20 ft multiplies by 8.

A site plan shows a sewer invert of 105.00 ft upstream and 104.40 ft downstream over a 40 ft run. What is the slope in inches per foot?

• a.0.018 in per ft
• b.0.125 in per ft
• c.0.18 in per ft✓
• d.0.15 in per ft

The fall is 105.00 - 104.40 = 0.60 ft = 7.2 in, and 7.2 in / 40 ft = 0.18 in per ft. 0.018 is the value in feet per foot (off by a factor of 12), and 0.125 (1/8 in per ft) would give only 5 in of fall over 40 ft.

A building sewer runs 50 ft at 1/4 in per ft. The upstream invert is 100.00 ft. What is the downstream invert elevation?

• a.99.48 ft
• b.98.96 ft✓
• c.101.04 ft
• d.98.75 ft

Fall = 50 ft x 1/4 in = 12.5 in = 1.04 ft, so 100.00 - 1.04 = 98.96 ft. 99.48 ft halves the fall (as if 1/8 in per ft), 101.04 ft runs the sewer uphill, and 98.75 ft rounds the fall incorrectly.

A 8 ft deep trench with a 4 ft wide bottom is dug in Type B soil and sloped at 1 to 1. How wide must the excavation be at the top?

• a.12 ft
• b.24 ft
• c.20 ft✓
• d.16 ft

Type B soil is sloped 1 horizontal to 1 vertical, so each wall lays back 1 x 8 = 8 ft. Both walls sloped gives 4 + 8 + 8 = 20 ft at the top (OSHA 1926 Subpart P, Appendix B). Adding the layback to one side only gives 12 ft, and Type C (1.5:1) would give 24 ft.

A 6 ft deep trench with a 3 ft wide bottom is dug in Type A soil and sloped at 3/4 to 1. How wide must the excavation be at the top?

• a.9 ft
• b.15 ft
• c.12 ft✓
• d.18 ft

Type A soil is sloped 3/4 horizontal to 1 vertical, so each wall lays back 0.75 x 6 = 4.5 ft. With both walls sloped, 3 + 4.5 + 4.5 = 12 ft at the top. Adding one layback gives 9 ft; a 1:1 slope would give 15 ft.

A trench 120 ft long and 5 ft deep has workers along its full length. What is the minimum number of ladders (or other means of egress) required?

• a.3✓
• b.1
• c.2
• d.5

In a trench 4 ft or deeper, a means of egress must be within 25 ft of lateral travel of every worker, so each ladder covers 50 ft of trench (OSHA 1926.651). 120 / 50 = 2.4, rounded up to 3 ladders. Two ladders leave workers more than 25 ft from egress.

How often must the competent person inspect an excavation where workers are exposed?

• a.Daily and before each shift, and after rain or other events that increase hazards✓
• b.Once a week
• c.Once a month
• d.Only at the start of the job

The competent person must inspect the excavation daily and before each shift, and again after any rainstorm or other hazard-increasing event, removing workers if a hazard is found (OSHA 1926.651(k)). Weekly or one-time inspection does not meet the rule.

Before entry into a confined space, the atmosphere reads 23.8 percent oxygen. What does this indicate?

• a.A safe, normal atmosphere
• b.An oxygen-enriched atmosphere, an increased fire and explosion hazard✓
• c.A meter error to be ignored
• d.An oxygen-deficient atmosphere

An acceptable atmosphere is 19.5 to 23.5 percent oxygen, so 23.8 percent is oxygen-enriched, which greatly increases fire and explosion risk and prohibits entry until corrected (OSHA 1910.146). It is neither normal nor deficient, and the reading must not be ignored.

Entry into a permit-required confined space such as a sewer manhole requires:

• a.Nothing special
• b.Only a filtering facepiece respirator and a co-worker standing nearby to watch the entrant
• c.Only a flashlight
• d.An entry permit, an attendant, atmospheric testing, and rescue/retrieval provisions✓

A permit-required confined space entry requires a signed entry permit, atmospheric testing, an attendant posted outside, and rescue/retrieval means, along with any needed ventilation and supplied-air respirators (OSHA 1910.146). A filtering facepiece cannot add oxygen and is not sufficient.

What personal protective equipment is required when cutting or grinding pipe?

• a.Eye and face protection such as safety glasses or a face shield✓
• b.Only gloves
• c.Only a hard hat
• d.No PPE is needed

Cutting and grinding throw chips and sparks, so eye and face protection is required, and a face shield is added over safety glasses for grinding (OSHA 1926.102). Gloves or a hard hat alone do not protect the eyes.

A portable ladder used to access a landing (such as the top of a trench) must extend above the landing surface by at least:

• a.6 in
• b.3 ft✓
• c.6 ft
• d.1 ft

A portable ladder used for access must extend at least 3 ft above the upper landing so a worker has something to hold while stepping off (OSHA 1926.1053). 1 ft or 6 in leaves nothing to grasp at the top.

Portable electric power tools on a construction site must be protected by:

• a.Nothing
• b.GFCI protection (or an assured equipment grounding conductor program)✓
• c.A fuse only
• d.A household power strip

Receptacles supplying portable tools on a jobsite must have ground-fault circuit-interrupter protection, or the employer must run an assured equipment grounding conductor program (OSHA 1926.404). A fuse or a power strip does not protect against electrocution.

Where do you find the hazard and handling information for PVC primer and solvent cement?

• a.The building permit
• b.The plumbing code book
• c.The Safety Data Sheet (SDS)✓
• d.The supplier invoice

The Safety Data Sheet (SDS) provides the flammability, exposure, first-aid, and handling information for chemical products such as primer and cement, and must be available to workers under the Hazard Communication standard (OSHA 1910.1200). The permit and code do not carry that data.

ABS and PVC DWV pipe are joined by:

• a.Solvent cement, using the primer and cement listed for the material✓
• b.Soldered joints
• c.Crimp rings
• d.Threaded joints

Rigid plastic DWV pipe is joined with solvent cement, with PVC requiring a primer and PVC cement and ABS using ABS cement (never interchanged). Threading, soldering, and crimping apply to metal or flexible materials, not solvent-welded plastic.

A hub-and-spigot (bell-and-spigot) cast-iron soil pipe joint is made with:

• a.A compression (rubber) gasket, or molten lead and oakum✓
• b.A wax ring
• c.Pipe-thread dope
• d.Solvent cement

A hub-and-spigot cast-iron joint is made either with a compression rubber gasket pushed into the hub or, in the traditional method, with oakum packing caulked and molten lead poured over it. Solvent cement, wax rings, and thread dope are for other materials and fittings.

Copper tube is joined by:

• a.Solvent cement
• b.Crimp rings only
• c.Threaded joints only
• d.Soldered or brazed joints, or approved press or mechanical fittings✓

Copper tube is joined by soldering or brazing, or with listed press and mechanical fittings (IPC 605). Solvent cement is for plastic, copper water tube is not field-threaded, and crimp rings are a PEX method.

Piping run through a wood stud less than 1-1/4 in from the edge must be protected by:

• a.A larger drill bit
• b.Nothing
• c.A steel nail (shield) plate✓
• d.A wrap of tape

Where a pipe is closer than 1-1/4 in to the edge of a stud or plate, a steel nail plate (shield plate) must cover the area to stop nails and screws from puncturing the pipe (IPC 305.6). Tape provides no such protection.

A pipe that penetrates a fire-rated wall or floor assembly must be:

• a.Left open around the pipe
• b.Wrapped in cloth
• c.Coated with grease
• d.Sealed with an approved firestop system that maintains the fire rating✓

A penetration of a fire-rated assembly must be sealed with a tested, approved firestop system so the assembly keeps its fire-resistance rating (IPC 305 / IBC firestopping). Leaving the annular space open, or stuffing it with cloth, defeats the rating.