Journeyman Plumbers Exam Drainage, Waste, and Venting 5 — Questions and Answers
Question 1: When testing a DWV system with water, to what height must the water column be maintained above the highest point of the system?
- 3 feet
- 5 feet
- 10 feet (Correct answer)
- The entire system must be filled to the highest vent opening
Correct answer: 10 feet
A water test requires the system to be filled to a 10-foot head of water above the highest point being tested, per the UPC.
Question 2: What is a 'P-trap'?
- A trap shaped like the letter P used for pressure balancing
- A fixture trap with a water seal that prevents sewer gas entry (Correct answer)
- A cleanout plug at the base of a vertical stack
- A pressure-testing fitting used during inspection
Correct answer: A fixture trap with a water seal that prevents sewer gas entry
A P-trap is the standard fixture trap that maintains a water seal to prevent sewer gases from entering the building through fixture drains.
Question 3: A soil pipe carries which type of waste?
- Only gray water from sinks and showers
- Human waste and urine from water closets and urinals (Correct answer)
- Storm water and roof drainage only
- Chemical waste from industrial processes
Correct answer: Human waste and urine from water closets and urinals
A soil pipe is defined as a pipe that conveys the discharge of water closets and urinals, with or without other waste.
Question 4: What is the minimum size of a building sewer that receives discharge from a water closet?
- 2 inches
- 3 inches
- 4 inches (Correct answer)
- 6 inches
Correct answer: 4 inches
The minimum building sewer size that receives water closet discharge is 4 inches per the UPC.
Question 5: Which venting arrangement is used when a vent pipe must be routed under a slab before it can rise to open air?
- This configuration is never permitted
- An engineered vent system approved by the AHJ (Correct answer)
- A Chicago loop or return vent configuration
- Install an AAV at the fixture instead
Correct answer: An engineered vent system approved by the AHJ
When a vent must pass under a slab, an engineered vent system specifically approved by the authority having jurisdiction (AHJ) is required.
Question 6: What is the purpose of a cleanout installed at the base of a soil stack?
- To provide a fresh air inlet to the stack
- To allow rodding and clearing of the building drain and stack (Correct answer)
- To act as a pressure relief for the system
- To provide a test connection point only
Correct answer: To allow rodding and clearing of the building drain and stack
A cleanout at the base of a soil stack provides access for drain-cleaning equipment to clear blockages in the stack and building drain.
Question 7: When a vent pipe passes through a roof, what is the minimum height it must extend above the roof surface in a climate with heavy snowfall?
- 2 inches
- 6 inches
- 12 inches
- At least 12 inches and checked against local frost/snow depth requirements (Correct answer)
Correct answer: At least 12 inches and checked against local frost/snow depth requirements
In heavy snowfall areas, vent pipes must extend at least 12 inches above the roof and may need to be higher per local codes to prevent snow from blocking the vent opening.
Journeyman Plumbers Exam Drainage, Waste, and Venting 5
When testing a DWV system with water, to what height must the water column be maintained above the highest point of the system?