Journeyman Plumbers Exam Venting and Backflow Prevention 2 — Questions and Answers
Question 1: What is the minimum diameter for a vent pipe serving a 3-inch drain pipe under the IPC?
- 1 inch
- 1.5 inches (Correct answer)
- 2 inches
- 3 inches
Correct answer: 1.5 inches
The vent pipe must be at least half the diameter of the drain it serves, with a minimum of 1.25 inches, making 1.5 inches the standard minimum for a 3-inch drain.
Question 2: A circuit vent is connected to a horizontal branch drain at what location relative to the fixture connections?
- Downstream of the last fixture (Correct answer)
- Upstream of the first fixture
- Between the first and last fixtures
- At the stack connection
Correct answer: Downstream of the last fixture
A circuit vent connects to the horizontal branch drain downstream (below) the last fixture connection on that branch.
Question 3: What type of backflow preventer is required on a hose bibb supplying potable water?
- Double check valve
- Reduced pressure zone device
- Vacuum breaker (Correct answer)
- Air gap
Correct answer: Vacuum breaker
A hose-connection vacuum breaker (HCVB) is required on hose bibbs to prevent siphonage of potentially contaminated water back into the supply.
Question 4: Under which condition is a wet vent system NOT permitted?
- When serving only bathroom groups
- When the drain serves more than one floor (Correct answer)
- When fixture units exceed 4
- When used with individual vents
Correct answer: When the drain serves more than one floor
Wet venting is generally limited to a single story; drains serving fixtures on multiple floors require conventional venting.
Question 5: Which device provides the highest level of backflow protection and is required for high-hazard connections?
- Pressure vacuum breaker
- Double check valve assembly
- Reduced pressure zone (RPZ) assembly (Correct answer)
- Atmospheric vacuum breaker
Correct answer: Reduced pressure zone (RPZ) assembly
The reduced pressure zone assembly is the highest-rated mechanical backflow preventer and is required for high-hazard cross-connections such as chemical feed lines.
Question 6: How far must a vent pipe terminal extend above a roof that is used for purposes other than weather protection?
- 6 inches
- 12 inches
- 7 feet (Correct answer)
- 10 feet
Correct answer: 7 feet
When a roof is used as a deck, garden, or other occupied space, vent terminals must extend at least 7 feet above the roof surface to protect occupants from sewer gases.
Question 7: What is the purpose of a running trap installed on a building drain?
- To prevent backflow of sewer gases into the building (Correct answer)
- To allow air to enter the drain system
- To separate stormwater from sewage
- To reduce drain velocity
Correct answer: To prevent backflow of sewer gases into the building
A running trap (house trap) provides a water seal between the building drain and the public sewer to block sewer gases from entering the building.
Journeyman Plumbers Exam Venting and Backflow Prevention 2
What is the minimum diameter for a vent pipe serving a 3-inch drain pipe under the IPC?