Venting: Washington Journey Level Plumber Practice Questions
Vent terminals, connections and grades, trap-to-vent distance, vent sizing, wet, circuit, island and combination venting, AAVs.
Often missed
Question 1
What is the main purpose of a plumbing vent system?
Correct answer: To protect trap seals
IPC 2021 901.2 / UPC 2021 901.2
Vents let air in and out of the drainage system so the flow of waste does not suck or push the water out of the traps; they also carry sewer gas outdoors.
Question 2
How many vent pipes must extend to the outdoors from a building's drainage system?
Correct answer: At least one
IPC 2021 904.1 / UPC 2021 901
Every building drainage system needs at least one vent extending to the outdoors to relieve positive pressure; AAVs cannot replace it.
Question 3
Under the UPC, a vent through the roof must end at least how high above the roof?
Correct answer: 6 inches
UPC 2021 906.1
The UPC requires vents to extend at least 6 inches above the roof and stand at least 12 inches from any vertical surface.
Question 4
A roof is used as a deck where people gather. How high must vent pipes extend above it?
Correct answer: 7 ft
IPC 2021 903.1.2 / UPC 2021 906.3
Where a roof is used for assembly, recreation or similar purposes, vents must rise at least 7 ft above it so sewer gas is released above people's heads.
Question 5
A vent terminal is 6 ft horizontally from an operable window. How high above the top of the window must it be?
Correct answer: At least 3 ft
IPC 2021 903.5 / UPC 2021 906.2
Vent terminals within 10 ft horizontally of a door, operable window or air intake must be at least 3 ft above its top, and never directly beneath it.
Question 6
Which vent terminal location is prohibited?
Correct answer: Directly below an operable window
IPC 2021 903.5 / UPC 2021 906.2
A vent may never end directly beneath a door, operable window or air intake. Beyond 10 ft horizontally, or 3 ft above the top of the opening, it is acceptable.
Question 7
A vent pipe extending through the roof is used to hold up a TV antenna. Is this allowed?
Correct answer: No, it may not support anything
IPC 2021 903 / UPC 2021 906
Vent terminals may not be used as flagpoles, antenna masts or supports; the load can break joints and flashing.
Question 8
How must horizontal vent piping be graded?
Correct answer: To drain back to the drain it serves
IPC 2021 905.2 / UPC 2021 905.1
Vents collect condensation and rain, so they slope back to drain by gravity into the drainage system.
Question 9
Where must a dry vent connect to a horizontal drain?
Correct answer: Above the centerline of the drain
IPC 2021 905.3 / UPC 2021 905.2
A dry vent taken off below the centerline would fill with waste and clog; it must connect above the centerline, rising at an angle toward vertical.
Question 10
A dry vent rises from a lavatory drain. How high must it rise before it turns horizontal?
Correct answer: 6 inches above the flood level rim
IPC 2021 905.4 / UPC 2021 905.3
Rising 6 inches above the flood level rim before going horizontal keeps the horizontal vent from becoming a drain if the fixture backs up.
Question 11
A branch vent connects to a vent stack. How high must the connection be?
Correct answer: 6 inches above the highest fixture's flood rim
IPC 2021 905.5 / UPC 2021 905.3
The connection to the vent stack or stack vent is kept at least 6 inches above the highest fixture's flood level rim, so a backup cannot enter the vent.
Question 12
Under the UPC, what is the maximum length of a 1-1/2-inch trap arm?
Correct answer: 3 ft 6 in
UPC 2021 1002.2
The UPC limits a 1-1/2-inch trap arm to 3 ft 6 in from the trap weir to the vent. The IPC allows 6 ft.
Question 13
Under the UPC, what is the maximum length of a 2-inch trap arm?
Correct answer: 5 ft
UPC 2021 1002.2
The UPC limits a 2-inch trap arm to 5 ft. The IPC allows 8 ft for a 2-inch fixture drain.
Question 14
Under the UPC, what is the maximum length of a 3-inch trap arm?
Correct answer: 6 ft
UPC 2021 1002.2
The UPC limits a 3-inch trap arm to 6 ft. The IPC allows 12 ft.
Question 15
What is the minimum distance between a trap weir and the vent connection?
Correct answer: Two pipe diameters
IPC 2021 909.3 / UPC 2021 1002.2
A vent closer than two pipe diameters to the weir acts like a crown vent and clogs. Both codes require at least two diameters.
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Practice questions are written in our own words and cite code sections by number. Always study from your own copy of the code and the official candidate bulletin.