Master Plumber Exam Drainage, Waste, and Venting 2 — Questions and Answers
Question 1: What is the minimum slope required for a 3-inch horizontal drain pipe under the IPC?
- 1/16 inch per foot
- 1/8 inch per foot (Correct answer)
- 1/4 inch per foot
- 1/2 inch per foot
Correct answer: 1/8 inch per foot
The IPC requires a minimum slope of 1/8 inch per foot for 3-inch horizontal drain pipes to ensure proper flow.
Question 2: Which type of vent serves as both a vent for a trap and the drain for a fixture?
- Common vent
- Wet vent (Correct answer)
- Air admittance valve
- Circuit vent
Correct answer: Wet vent
A wet vent simultaneously carries waste water from one fixture and provides the vent for another fixture's trap.
Question 3: Under the IPC, what is the maximum distance a P-trap for a lavatory can be from its vent?
- 2 feet
- 4 feet (Correct answer)
- 6 feet
- 8 feet
Correct answer: 4 feet
The IPC allows a maximum developed length of 4 feet between a lavatory trap and its vent connection.
Question 4: A building drain that transitions to a building sewer must maintain the same slope unless:
- The sewer is cast iron
- A cleanout is installed at the junction
- The sewer pipe is larger in diameter (Correct answer)
- The transition occurs outside the foundation
Correct answer: The sewer pipe is larger in diameter
When the building sewer pipe is larger than the building drain, a change in slope is permissible at the transition point.
Question 5: Which fitting is prohibited for use in a horizontal-to-vertical drain change of direction?
- Long-sweep quarter bend
- Short-sweep quarter bend
- Combination wye and eighth bend
- Sanitary tee used on its side (Correct answer)
Correct answer: Sanitary tee used on its side
A sanitary tee used on its side (horizontal flow) is prohibited because its design creates turbulence and restricts drainage flow.
Question 6: What is the primary purpose of a relief vent in a drainage system?
- To provide fresh air to a trap
- To equalize pressure between the vent stack and drain stack (Correct answer)
- To serve as an emergency overflow path
- To vent a fixture that cannot reach the main stack
Correct answer: To equalize pressure between the vent stack and drain stack
A relief vent provides a pressure-equalizing connection between the drain stack and the vent stack to prevent pressure buildup.
Question 7: Under the IPC, air admittance valves (AAVs) are NOT permitted to be used as the sole vent for:
- Lavatories
- Kitchen sinks
- Sumps and ejectors (Correct answer)
- Laundry tubs
Correct answer: Sumps and ejectors
AAVs cannot be used as the sole vent for sumps and ejectors because these systems require outdoor venting to release sewer gases from the pit.
Master Plumber Exam Drainage, Waste, and Venting 2
What is the minimum slope required for a 3-inch horizontal drain pipe under the IPC?