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.