Venting: Colorado Journeyworker Plumber Practice Questions

What is the main purpose of a plumbing vent system?

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.

How many vent pipes must extend to the outdoors from a building's drainage system?

Every building drainage system needs at least one vent extending to the outdoors to relieve positive pressure; AAVs cannot replace it.

Under the model IPC, how far above the roof must an open vent pipe extend?

The model IPC leaves the roof extension height as a blank that each jurisdiction fills in (for example, Ohio uses 12 inches). The UPC sets 6 inches.

A roof is used as a deck where people gather. How high must vent pipes extend above it?

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.

A vent terminal is 6 ft horizontally from an operable window. How high above the top of the window must it be?

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.

Which vent terminal location is prohibited?

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.

Under the IPC, a vent terminal that extends through a side wall must be at least how far from a lot line and how high above the highest adjacent grade within 10 ft?

Side-wall vent terminals must be at least 10 ft from the lot line and 10 ft above the highest adjacent grade within 10 ft horizontally, and not under a building overhang with soffit vents.

Under the IPC, in a cold climate where frost could close a vent, what is the minimum vent size through the roof?

The IPC requires vents through the roof to be at least 3 inches in frost-closure areas, with the size increase made at least 1 ft inside the thermal envelope of the building.

A vent pipe extending through the roof is used to hold up a TV antenna. Is this allowed?

Vent terminals may not be used as flagpoles, antenna masts or supports; the load can break joints and flashing.

How must horizontal vent piping be graded?

Vents collect condensation and rain, so they slope back to drain by gravity into the drainage system.

Where must a dry vent connect to a horizontal drain?

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.

A dry vent rises from a lavatory drain. How high must it rise before it turns horizontal?

Rising 6 inches above the flood level rim before going horizontal keeps the horizontal vent from becoming a drain if the fixture backs up.

A branch vent connects to a vent stack. How high must the connection be?

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.

Under the IPC, what is the maximum developed length from the trap weir to the vent for a 1-1/2-inch fixture drain at 1/4 inch per foot?

The IPC trap-to-vent table allows 6 ft for a 1-1/2-inch fixture drain. The UPC trap arm limit for the same size is 3 ft 6 in.

Under the IPC, what is the maximum developed length from trap weir to vent for a 2-inch fixture drain at 1/4 inch per foot?

The IPC allows 8 ft for a 2-inch fixture drain. The UPC trap arm limit for 2 inches is 5 ft.