Journeyman Plumbers Exam Drainage, Waste, and Venting 2 — Questions and Answers
Question 1: What is the minimum slope required for a 3-inch horizontal drain pipe per the Uniform Plumbing Code?
- 1/8 inch per foot
- 1/4 inch per foot (Correct answer)
- 1/2 inch per foot
- 3/8 inch per foot
Correct answer: 1/4 inch per foot
The UPC requires 1/4 inch per foot (2% grade) slope for horizontal drain pipes 3 inches and larger.
Question 2: A wet vent is permitted to serve which combination of fixtures?
- Water closet and kitchen sink only
- Bathtub and lavatory on the same floor level (Correct answer)
- Two water closets on different floors
- Clothes washer and dishwasher only
Correct answer: Bathtub and lavatory on the same floor level
A wet vent commonly serves a bathtub and lavatory located on the same floor, where the drain also acts as the vent.
Question 3: When installing a drum trap, where must the outlet be located relative to the inlet?
- At the same level as the inlet
- Below the inlet
- At least 2 inches above the inlet (Correct answer)
- At the top of the trap body
Correct answer: At least 2 inches above the inlet
The outlet of a drum trap must be located at least 2 inches above the inlet to maintain the water seal.
Question 4: Which type of vent is installed on the downstream side of a fixture trap to prevent siphoning?
- Common vent
- Relief vent
- Back vent (individual vent) (Correct answer)
- Circuit vent
Correct answer: Back vent (individual vent)
A back vent, also called an individual vent, connects to the fixture drain on the downstream side of the trap to prevent trap siphoning.
Question 5: What is the maximum developed length of a 1.5-inch trap arm from trap weir to vent?
- 30 inches
- 42 inches (Correct answer)
- 54 inches
- 60 inches
Correct answer: 42 inches
Per the UPC, a 1.5-inch trap arm has a maximum developed length of 42 inches (3.5 feet) from the trap weir to the vent.
Question 6: A sanitary tee may be used in a drainage system in which orientation?
- On its back in a horizontal run
- In a vertical stack receiving horizontal branch connections (Correct answer)
- Horizontally with the branch pointing up
- As a horizontal-to-horizontal fitting only
Correct answer: In a vertical stack receiving horizontal branch connections
Sanitary tees are approved for use in the vertical position where a horizontal branch connects to a vertical stack.
Question 7: What is the minimum number of fixture units a 4-inch building drain can carry at 1/4-inch-per-foot slope?
- 96 DFUs
- 160 DFUs (Correct answer)
- 216 DFUs
- 250 DFUs
Correct answer: 160 DFUs
A 4-inch building drain sloped at 1/4 inch per foot has a rated capacity of 160 drainage fixture units (DFUs) per the UPC drainage load tables.
Journeyman Plumbers Exam Drainage, Waste, and Venting 2
What is the minimum slope required for a 3-inch horizontal drain pipe per the Uniform Plumbing Code?