CSLB General Building (B) — 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.1-1/8 in
• b.2-1/4 in
• c.4-1/2 in✓
• d.9 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

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.2-1/2 ft
• c.5 ft
• d.6 ft

The trap arm table allows 3-1/2 ft of developed length for a 1-1/2 in trap arm. 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, so each of those is the wrong row of the table.

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

• a.1 in to 2 in
• b.1-1/2 in to 3 in
• c.2 in to 6 in
• d.2 in to 4 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.12 in✓
• c.24 in
• d.48 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 in
• b.1-1/4 in✓
• c.1-1/2 in
• d.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 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.

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 backwater valve
• b.A relief vent
• c.A cleanout✓
• 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 in
• c.1-1/2 in
• d.2 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.

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

• a.An S-trap✓
• b.A P-trap vented within the permitted trap arm length
• 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.99.85 ft
• b.99.90 ft
• c.99.25 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.6 in✓
• c.12 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.4 ft horizontally from the window with the terminal level with the sill
• b.6 ft horizontally from the window with the terminal 1 ft above the top
• c.8 ft horizontally from the window with the terminal at the same height
• d.11 ft horizontally from the window✓

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

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

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.3✓
• c.4
• d.6

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

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.6 in
• b.8 in
• c.18 in
• d.12 in✓

Cleanouts on 2 in and smaller pipe require at least 12 in of clearance in front of the opening for rodding, while pipe larger than 2 in requires 18 in. The 18 in figure is the wrong pipe-size row here, and 6 in and 8 in are below any code clearance.

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

• a.4 in✓
• b.3 in
• c.5 in
• d.6 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.At the face of the exterior wall
• b.At the property line
• c.5 ft outside the building wall
• d.2 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.Reducing the vent one pipe size
• b.Increasing the vent one pipe size for its entire developed length✓
• c.Installing a trap primer at the base
• d.Sloping the vent at 1/4 in per ft

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 common vent✓
• b.A circuit vent
• c.A relief 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.Circuit vent
• b.Yoke vent
• c.Vent stack
• d.Island or loop 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 must be accessible and located above the fixture trap weir✓
• d.It replaces the need for any vent open to the atmosphere in the building

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.24 in✓
• c.30 in
• d.36 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.

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 backwater valve into the building sewer
• d.Through a double trap arrangement

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

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.18 ft
• b.24 ft
• c.36 ft✓
• d.54 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 building drain sloped at 1/4 in per ft compared with the same drain at 1/8 in per ft✓
• b.A horizontal fixture branch compared with a building drain of the same size
• c.A vent stack compared with a drainage stack of the same size
• d.A trap arm compared with a fixture branch of the same size

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.7 DFU
• b.9 DFU✓
• c.11 DFU
• d.12 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.1-1/2 in
• b.2 in
• c.2-1/2 in
• d.3 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.

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.Acceptable, because any trap arm may run 5 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.Not acceptable, because a 1-1/4 in trap arm is limited to 2 ft

The maximum developed length for a 1-1/4 in trap arm is 2-1/2 ft, so a 3 ft run exceeds the limit and the arm would need to be increased in size or the vent moved closer. The 5 ft figure belongs to a 2 in arm, no size is exempt from the table, and the 2 ft value understates the actual 2-1/2 ft limit.

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.Circuit vent✓
• b.Common vent
• c.Island vent
• d.Individual 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.12-1/2 in, and the slope may be permitted for 8 in and larger pipe where approved✓
• c.25 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 relief vent, limited to one fixture
• b.A yoke vent, limited to stacks over 10 stories
• c.A wet vent, limited to the fixtures and sizes the code specifically allows✓
• d.A loop vent, limited to island fixtures only

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 60.2 psi
• b.About 58.4 psi
• c.About 54.1 psi✓
• d.About 46.2 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 50.8 ft✓
• b.About 9.5 ft
• c.About 45.4 ft
• d.About 22 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 in
• b.1-1/2 in
• c.3 in
• d.2 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.3/4 in
• b.1 in✓
• c.1-1/4 in
• d.2 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 pressure-reducing valve limiting downstream pressure to not more than 80 psi✓
• b.Nothing, because the pressure is still under 100 psi
• c.An increase of one pipe size on the water service
• d.An approved vacuum relief valve 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.5 hangers
• b.6 hangers
• c.7 hangers✓
• d.8 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.6 supports
• b.8 supports✓
• c.9 supports
• d.12 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.3 supports
• b.4 supports
• c.5 supports
• d.6 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.5 feet per second✓
• b.8 feet per second
• c.10 feet per second
• d.12 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 larger supply pipe to slow the water velocity
• b.Approved water hammer arrestors sized and located per the manufacturer's instructions✓
• c.A check valve immediately upstream of each valve
• d.A vacuum breaker on each supply branch

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.Double check valve assembly
• b.Atmospheric vacuum breaker
• c.Reduced pressure principle backflow preventer✓
• d.Hose bibb vacuum breaker

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

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.34 in
• b.40 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.4 ft 0 in
• c.3 ft 6 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.The outlet is a hose thread connection
• b.The device would be located outdoors
• c.The supply piping is copper rather than steel
• d.A booster pump downstream could push water back toward the supply✓

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

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.0.2 percent✓
• b.0.25 percent
• c.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.0.2 percent
• b.0.05 percent
• c.0.25 percent✓
• d.8 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 36.7 psi✓
• c.About 48.0 psi
• d.About 25.5 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 25.3 psi
• c.About 14.7 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 15 psi per 100 ft
• b.About 6.7 psi per 100 ft
• c.About 10 psi per 100 ft✓
• d.About 24 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.15.5 WSFU✓
• b.14.5 WSFU
• c.16.5 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 exactly doubles
• b.The demand in gpm increases by less than double✓
• c.The demand in gpm more than 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.1/2 in
• b.5/8 in
• c.1 in
• d.3/4 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 44.1 psi✓
• b.About 32.0 psi
• c.About 55.1 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 4.4 fps
• b.About 6.0 fps
• c.About 7.9 fps✓
• d.About 10.2 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 0.6 in
• b.About 1.0 in
• c.About 2.4 in
• d.About 1.7 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.A brass compression coupling
• b.An approved dielectric fitting or dielectric union✓
• c.A soldered joint made directly to the steel pipe
• d.A rubber sleeve coupling with stainless steel clamps

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.15 inches✓
• d.18 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.30 inches✓
• b.24 inches
• c.21 inches
• d.36 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.No, a compartment must be at least 36 inches wide in all cases
• c.Yes, but only because a compartment is exempt from side clearance rules
• d.Yes, the centerline is 16 inches from each side, which exceeds the 15 inch minimum✓

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.15 inches
• b.21 inches✓
• c.24 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.2,560 gallons
• b.3,500 gallons
• c.5,120 gallons
• d.4,440 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 combination temperature and pressure relief valve✓
• b.A vacuum relief valve at the top of the tank
• c.A backflow preventer on the cold water inlet
• d.A pressure reducing valve on the building supply

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

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.1/2 inch
• b.5/8 inch
• c.3/4 inch✓
• d.1 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.Directly across the control housing
• b.At least 4 inches below the controls
• c.At the exact vertical midpoint of the tank
• d.At least 4 inches above the controls✓

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.12 inches
• c.24 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.30 square inches✓
• c.60 square inches
• d.12 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.2,000 cubic feet
• b.3,000 cubic feet
• c.5,000 cubic feet✓
• d.10,000 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.Both within 12 inches of the ceiling of the enclosure
• b.Both within 12 inches of the floor of the enclosure
• c.One at the ceiling and one at any convenient height on an outside wall
• d.One within 12 inches of the top of the enclosure and one within 12 inches of the bottom✓

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

32 times 32 equals 1,024 square inches, which is exactly the minimum area, and each interior dimension of 32 inches clears the 30 inch minimum. The area minimum is 1,024 square inches, not 1,200, and there is no universal 36 inch interior dimension for a standard shower. Shower doors must provide a 22 inch clear opening, so a 30 inch door is not the condition that makes the stall compliant.

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.1 inch
• b.2 inches
• c.3 inches✓
• d.1-1/2 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.3/4 inch
• b.1 inch✓
• c.1-1/2 inches
• d.3/8 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.Yes, 14 inches is within the allowable range
• c.No, the standpipe must extend at least 18 inches and not more than 42 inches above the trap weir✓
• d.No, the standpipe must be at least 24 inches and not more than 60 inches above the trap weir

A clothes washer standpipe must be a minimum of 18 inches and a maximum of 42 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. The 24 to 60 inch range in the last choice is not the code window.

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.17.6 gallons
• c.24.0 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.0.5 gallon
• c.1.0 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.Set the flange below the finished floor and shim the bowl with wood blocks
• b.Set the flange on top of the finished floor, secure it to the structure with fasteners, and seal with a wax or approved gasket✓
• c.Seal the flange to the bowl with structural adhesive instead of fasteners
• d.Rely on the closet bolts alone to hold the flange to the floor

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.500 gallons
• c.750 gallons✓
• d.1,500 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.No action; cleaning is required only at 50 percent
• b.Add an enzyme treatment and re-inspect in six months
• c.Install a larger flow control device to slow the incoming flow
• d.Pump and clean the interceptor, since the 25 percent threshold has been reached✓

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

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 through a P-trap with no air gap or air break
• b.Indirectly connected through an air gap to an approved receptor✓
• c.Directly connected but only through a grease interceptor
• 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.132 cfh
• b.175 cfh✓
• c.70 cfh
• d.1,750 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.70 cfh✓
• b.175 cfh
• c.437 cfh
• d.44 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.12 ft, the actual length of section A
• b.30 ft, the length from the meter through section B
• c.23 ft, the average of the three sections
• d.65 ft, the total length from the meter to the farthest outlet✓

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

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.2 psi
• c.7 in w.c.
• d.11 in w.c.

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

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

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.14 AWG
• b.12 AWG
• c.6 AWG✓
• d.10 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.0.375 psi, which is 1.5 times the working pressure
• b.3 psi✓
• c.10 psi
• 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.5 minutes
• c.30 minutes
• d.24 hours

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

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 the connector passes through the cabinet wall behind the range
• c.It is allowed only if a second connector is added to reach the valve
• 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.Polyethylene (PE) pipe✓
• b.Schedule 40 black steel pipe
• c.Corrugated stainless steel tubing
• d.Type L copper tube

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.1,830,000 Btu
• b.18,300,000 Btu✓
• c.183,000,000 Btu
• d.457,500 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 23 hours
• b.About 92 hours
• c.About 46 hours✓
• d.About 4.6 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.105 cfh at 90 ft✓
• b.65 cfh at 90 ft
• c.175 cfh at 15 ft
• d.105 cfh at 15 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 into the concrete with no sleeve
• b.A union must be installed inside the wall for future service
• c.The pipe may be run through the wall only if it is PE
• d.The pipe must be protected against corrosion and breakage, typically by a sleeve sealed at one end✓

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

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

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

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

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.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✓
• b.The system is filled to a 5 ft head and held for 5 minutes, and a small drop is acceptable if no leak is visible
• 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.28 ft, which is the height of the highest joint in the section under test
• b.30 ft
• c.33 ft
• d.38 ft✓

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.3 psi held for 10 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.50 psi held for 15 minutes

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 the test pressure of 48 psi exceeded the 45 psi working pressure of the system
• b.Fail, because the test must be at the working pressure but not less than 50 psi and must hold for 15 minutes with no drop✓
• c.Pass, because a 2 psi drop over 15 minutes is within the allowable tolerance for a supply test
• d.Fail, because a water supply system may only be tested with compressed air at 100 psi

The supply test is run at the system's working pressure but never less than 50 psi, and it must hold for at least 15 minutes without a loss of pressure, so a 48 psi start that falls to 46 psi fails on both counts. Exceeding the working pressure alone is not enough when the code sets a 50 psi floor. There is no allowable pressure drop; any drop indicates a leak. Air may be permitted as an alternate test medium in some jurisdictions, but it is not the only method and 100 psi is not the required value.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 riser or isometric diagram✓
• b.The floor plan view
• 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.10 ft 6 in
• c.14 ft✓
• d.17 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.0.0125 in per ft
• b.0.10 in per ft
• c.0.125 in per ft
• d.0.15 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.98.71 ft✓
• b.98.45 ft
• c.99.35 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.A warning line at the top of the trench and a spotter watching the walls are sufficient at this depth
• 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.The competent person may waive protection if the trench will be open for less than one work shift

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.13 ft 6 in
• b.24 ft✓
• c.17 ft
• 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.Two, placed so that no worker has more than 25 ft of lateral travel to reach a means of egress✓
• b.None, because a ladder is required only in trenches 6 ft deep or greater
• c.One, placed at the midpoint of the trench
• d.Four, one for every 25 ft of trench length

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.The standard sloping tables may be used at any depth, and the spoil may be piled at the trench edge to serve as a barrier
• b.Sloping is prohibited over 20 ft so only a trench box may be used, and the spoil must be kept 1 ft back
• 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 indicates an oxygen-enriched atmosphere, and the correct order is flammables first, then oxygen, then toxics
• c.The reading is oxygen deficient, and the space must be tested for oxygen first, then flammable gases and vapors, then toxic contaminants✓
• d.The reading is acceptable as long as the entrant wears a filtering facepiece respirator and an attendant is posted

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.The acetylene regulator may be set to 20 psig to speed up the braze as long as the cylinder is chained upright
• b.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✓
• 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.Cut the insulation off with a utility knife, bag it, and continue with the repair
• b.Wet the insulation before removing it, since wetting eliminates the need for a licensed abatement contractor
• c.Disturb the insulation only while wearing a filtering facepiece, and reuse 50/50 solder so the new joints match the existing system
• d.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✓

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.