Journeyman Plumbers Exam Drainage, Waste, and Vent Systems 2 — Questions and Answers
Question 1: What is the minimum slope required for a 3-inch horizontal drain pipe under the IPC?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 1 inch per foot
Correct answer: 1/4 inch per foot
The IPC requires a minimum slope of 1/4 inch per foot for horizontal drain pipes 3 inches in diameter.
Question 2: A wet vent is permitted to serve which type of fixture combination?
- Water closet and kitchen sink only
- Bathtub and lavatory on the same floor level (Correct answer)
- Two water closets on separate floors
- Floor drain and clothes washer only
Correct answer: Bathtub and lavatory on the same floor level
A wet vent typically serves a lavatory and bathtub/shower combination where the drain pipe also functions as the vent for the upstream fixture.
Question 3: What is the primary purpose of a P-trap in a drainage system?
- To increase water velocity in the drain
- To maintain a water seal that blocks sewer gases (Correct answer)
- To allow air into the drain line
- To reduce the slope of the horizontal drain
Correct answer: To maintain a water seal that blocks sewer gases
A P-trap retains a water seal that prevents sewer gases and odors from entering the building through the fixture drain.
Question 4: Under the IPC, what is the maximum distance a trap can be located from its vent?
- 2 feet
- 6 feet
- The distance depends on the pipe size and slope (Correct answer)
- 10 feet for all pipe sizes
Correct answer: The distance depends on the pipe size and slope
The maximum trap-to-vent distance is determined by the pipe diameter — for example, 3.5 feet for a 1.25-inch pipe and 6 feet for a 2-inch pipe.
Question 5: Which fitting type is prohibited for use in a horizontal-to-horizontal drain change of direction?
- Long-sweep 90-degree elbow
- Sanitary tee used on its side (Correct answer)
- Wye fitting
- Combination wye-and-eighth bend
Correct answer: Sanitary tee used on its side
A sanitary tee used in a horizontal plane (on its side) does not provide proper flow direction and is prohibited for horizontal drainage.
Question 6: A stack vent is defined as:
- A separate pipe that only vents the main soil stack
- The extension of the soil or waste stack above the highest horizontal drain connection (Correct answer)
- A horizontal vent pipe connecting multiple fixture vents
- A vent that terminates inside the building using an air admittance valve
Correct answer: The extension of the soil or waste stack above the highest horizontal drain connection
A stack vent is the vertical extension of the drainage stack above the topmost fixture connection that terminates through the roof.
Question 7: When sizing a building drain, the total fixture unit load must be compared to which variable?
- The pipe material only
- The pipe diameter and slope (Correct answer)
- The building height
- The water supply pressure
Correct answer: The pipe diameter and slope
Building drain sizing tables in the IPC use both the pipe diameter and the installed slope to determine the maximum allowable drainage fixture unit load.
Journeyman Plumbers Exam Drainage, Waste, and Vent Systems 2
What is the minimum slope required for a 3-inch horizontal drain pipe under the IPC?