Master Plumber Exam Drainage, Waste, and Venting 3 — Questions and Answers
Question 1: What is the minimum diameter of a vent stack that serves a building drain receiving discharge from 5 or more water closets?
- 2 inches
- 3 inches
- 4 inches (Correct answer)
- 6 inches
Correct answer: 4 inches
The IPC requires a minimum 4-inch vent stack when the building drain receives discharge from 5 or more water closets.
Question 2: A combination drain and vent system is limited to which type of fixtures?
- Water closets and urinals only
- Floor drains and floor sinks only (Correct answer)
- Fixtures with a trap seal not exceeding 4 inches
- Fixtures with a maximum drain diameter of 3 inches
Correct answer: Floor drains and floor sinks only
Combination drain and vent systems under the IPC are restricted to floor drains and floor sinks due to their low flow rates.
Question 3: When a horizontal branch drain connects to a stack between the lowest floor branch and the building drain, what is this zone called?
- Critical zone (Correct answer)
- Offsets zone
- Relief zone
- Hydraulic jump zone
Correct answer: Critical zone
The critical zone is the area at the base of the stack where high-velocity waste creates pressure fluctuations that can affect trap seals.
Question 4: What is the maximum number of fixture units permitted on a 2-inch horizontal branch drain?
- 4
- 6 (Correct answer)
- 8
- 12
Correct answer: 6
The IPC allows a maximum of 6 fixture units on a 2-inch horizontal branch drain at a 1/4-inch per foot slope.
Question 5: Which venting method allows multiple fixtures on a horizontal branch to share a single vent at the end of the branch?
- Individual venting
- Circuit venting (Correct answer)
- Crown venting
- Loop venting
Correct answer: Circuit venting
Circuit venting uses one vent at the end or beginning of a horizontal branch to serve multiple fixtures connected to that branch.
Question 6: Under IPC, what is the minimum distance a vent terminal must be from a window, door, or other air intake opening?
- 3 feet (Correct answer)
- 5 feet
- 10 feet
- 15 feet
Correct answer: 3 feet
The IPC requires vent terminals to be at least 3 feet from any window, door, or mechanical air intake to prevent sewer gas entry into the building.
Question 7: Which material is NOT listed as an approved material for DWV piping under the IPC?
- ABS plastic pipe
- Galvanized steel pipe (Correct answer)
- Cast iron pipe
- PVC plastic pipe
Correct answer: Galvanized steel pipe
Galvanized steel pipe is not approved for drain, waste, and vent applications because it corrodes when exposed to sewer gases and waste water.
Master Plumber Exam Drainage, Waste, and Venting 3
What is the minimum diameter of a vent stack that serves a building drain receiving discharge from 5 or more water closets?