Journeyman Plumber ExamDrainage, Waste, and Venting (DWV) SystemsMedium
A plumber is installing a main stack vent that extends through the roof of a single-family dwelling. There is a window located on the roof directly above the vent pipe. What is the minimum required horizontal clearance between the vent terminal and any openable window, door, or other opening into the building?
- A12 inches
- B10 feet
- C3 feet
- D6 inches
Show answer & explanationAnswer & explanation
Correct answer: B. 10 feet
Plumbing codes (e.g., IPC 904.1, UPC 906.2) typically require vent terminals to be located at least 10 feet horizontally from any openable window, door, or other opening into the building, to prevent noxious sewer gases from entering the living space.
Why the other options are wrong
- A. 12 inches (1 foot) is also insufficient for proper dispersion of sewer gases.
- C. 3 feet is a common minimum for vent height above the roof, but not for horizontal clearance to openings.
- D. 6 inches is insufficient and would allow sewer gases to easily enter the building.
Vent Terminal Horizontal Clearance
The minimum horizontal distance required between the termination of a vent pipe above the roof and any openable window, door, or other building opening.
- Prevents sewer gases from entering the building's interior.
- Ensures proper dilution and dispersion of gases.
- Typically 10 feet according to major plumbing codes.
- Applies to all types of openings, including skylights.
Memory trick: Vents need space, so gases don't invade your place.