Journeyman Plumber (UPC/IPC) — All Questions

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

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

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

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

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

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

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

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

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

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

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

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

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

• a.3 in✓
• b.4 in
• c.1 in
• d.2 in

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

What is a yoke vent?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

In DWV terminology, a branch interval is:

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

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

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

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

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

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

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

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

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

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

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

Which three factors together size a horizontal storm drain?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

What is the minimum trap size for a kitchen sink?

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

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

What is the minimum trap size for a lavatory?

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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