Journeyman Plumbers Exam Drainage, Waste, and Venting 4 — Questions and Answers
Question 1: Which fitting is required when a drain changes direction from vertical to horizontal?
- Short-sweep 1/4 bend
- Long-sweep 1/4 bend or combination wye and 1/8 bend (Correct answer)
- Sanitary tee on its back
- Standard 90-degree elbow
Correct answer: Long-sweep 1/4 bend or combination wye and 1/8 bend
A long-sweep 1/4 bend or a combination wye and 1/8 bend is required when transitioning from vertical to horizontal to ensure smooth, non-turbulent flow.
Question 2: What is the maximum vertical distance a fixture drain may drop before connecting to the trap arm?
- There is no vertical limit
- The drain must connect directly to the trap with no vertical drop
- One pipe diameter
- The trap arm must be level or pitched to drain only (Correct answer)
Correct answer: The trap arm must be level or pitched to drain only
The trap arm must be level or pitched toward the drain at no more than 1/4 inch per foot — no section between the trap and vent may be vertical.
Question 3: A 3-inch soil stack may NOT receive the discharge from which fixture?
- Kitchen sink
- Water closet (Correct answer)
- Bathtub
- Lavatory
Correct answer: Water closet
Water closets require a minimum 3-inch drain, but the stack receiving water closet discharge must also be at least 3 inches — however the trap itself must be 3 inches minimum, making the stack size at least 3 inches; a 2-inch stack cannot receive a water closet.
Question 4: In a DWV system, what does the term 'developed length' mean?
- The straight-line distance between two points
- The total length measured along the centerline of the pipe including fittings (Correct answer)
- The vertical drop of a drain pipe
- The diameter multiplied by the run length
Correct answer: The total length measured along the centerline of the pipe including fittings
Developed length is the total length measured along the centerline of the pipe, following all bends and offsets, used for calculating vent lengths and trap arm limits.
Question 5: Which condition is considered a cross-connection in a DWV system?
- Two vent pipes tied together above the fixtures
- A drain pipe connected directly to a potable water supply pipe (Correct answer)
- A common vent serving two lavatories
- A soil stack receiving waste from multiple floors
Correct answer: A drain pipe connected directly to a potable water supply pipe
A cross-connection occurs when a drain pipe is directly connected to a potable water supply, creating a potential for contamination.
Question 6: What is the minimum horizontal distance required between a trap and its vent connection measured along the trap arm?
- No minimum — the vent can be directly at the trap outlet (Correct answer)
- 2 times the pipe diameter
- The distance must be at least the pipe diameter
- There is a minimum of 6 inches
Correct answer: No minimum — the vent can be directly at the trap outlet
There is no code-specified minimum distance between the trap outlet and the vent connection — the vent may connect immediately after the trap.
Question 7: Island fixture venting is a special technique used when a vent pipe cannot rise vertically because of which obstacle?
- A load-bearing wall above the fixture
- A ceiling or floor joist blocking the vent path
- A kitchen island with no wall access nearby (Correct answer)
- An exterior wall with insufficient clearance
Correct answer: A kitchen island with no wall access nearby
Island fixture venting is required for sinks in kitchen islands where no nearby wall is available for the vent pipe to rise through.
