Journeyman Plumbers Exam Venting and Backflow Prevention 3 — Questions and Answers
Question 1: An island fixture vent must loop to within how many inches of the underside of the counter?
- 1 inch
- 3 inches
- 6 inches (Correct answer)
- 12 inches
Correct answer: 6 inches
The island fixture vent must loop up to within 6 inches of the underside of the counter top before dropping back to connect to the drain.
Question 2: What is the maximum developed length of a 2-inch vent pipe serving a single water closet?
- 20 feet
- 30 feet
- 60 feet (Correct answer)
- 120 feet
Correct answer: 60 feet
Under the IPC, a 2-inch vent pipe serving a single water closet has a maximum developed length of 60 feet.
Question 3: A pressure vacuum breaker (PVB) differs from an atmospheric vacuum breaker (AVB) in that a PVB:
- Cannot be installed under continuous pressure
- Can be installed under continuous pressure (Correct answer)
- Requires a vertical installation only
- Does not contain an air inlet
Correct answer: Can be installed under continuous pressure
A pressure vacuum breaker can remain under continuous supply pressure, whereas an atmospheric vacuum breaker must be de-pressurized for at least 12 hours per day.
Question 4: Where must an air admittance valve (AAV) NOT be installed?
- In a wall cavity
- In an attic
- Below grade or in a sealed space without air (Correct answer)
- Above the flood level rim of a fixture
Correct answer: Below grade or in a sealed space without air
AAVs require access to air to function; they cannot be installed below grade or in any sealed space where air is unavailable.
Question 5: Which fixture is permitted to wet vent under most plumbing codes?
- Floor drain
- Kitchen sink in a commercial kitchen
- Bathroom group (lavatory, water closet, tub) on a single floor (Correct answer)
- Clothes washer standpipe
Correct answer: Bathroom group (lavatory, water closet, tub) on a single floor
A bathroom group on a single floor is the classic application of wet venting, where the lavatory drain serves as both a drain and a vent for the water closet.
Question 6: What is the minimum horizontal distance from a vent terminal opening to any window or door that can be opened?
- 2 feet
- 3 feet (Correct answer)
- 10 feet
- 5 feet
Correct answer: 3 feet
Vent terminal openings must be located at least 3 feet from any openable window, door, or other opening into the building.
Question 7: A double-check valve assembly (DCVA) is appropriate for which hazard level cross-connection?
- High hazard (toxic substances)
- Low hazard (non-toxic, non-health threat) (Correct answer)
- Any hazard level equally
- Only for fire suppression systems
Correct answer: Low hazard (non-toxic, non-health threat)
DCVAs are suitable for low-hazard cross-connections where backflow could cause aesthetic issues but not health risks; high-hazard applications require an RPZ.
