306A National Plumbing Code of Canada 6 — Questions and Answers
Question 1: What does the Code define as a 'wet vent'?
- A vent pipe that passes through a humid space
- A vent that also serves as a drain for one or more fixtures (Correct answer)
- A vent connected to a condensate line
- A vent that terminates below the roof line
Correct answer: A vent that also serves as a drain for one or more fixtures
A wet vent is defined as a vent pipe that also serves as a drain for one or more fixtures. It must be sized to handle both the drainage and venting functions.
Question 2: According to the Code, what size must a wet vent be if it serves a water closet?
- 1½ inch
- 2 inch
- 3 inch (Correct answer)
- 4 inch
Correct answer: 3 inch
A wet vent serving a water closet must be at least 3 inches in diameter to handle the combined drainage and venting load without restricting either function.
Question 3: What is the Code requirement for the grade of underground drainage piping?
- Level is acceptable if joints are sealed
- Minimum 1 in 50 for pipe 3 inches and smaller (Correct answer)
- All underground pipe must slope at 1 in 25
- Slope is only required for pipes over 4 inches
Correct answer: Minimum 1 in 50 for pipe 3 inches and smaller
Underground drainage pipe 3 inches and smaller requires a minimum grade of 1 in 50. Pipes 4 inches and larger may use a minimum grade of 1 in 100.
Question 4: According to the Code, what is the minimum size of a relief vent?
- Half the diameter of the pipe it serves (Correct answer)
- The same diameter as the vent stack it connects to
- 1½ inch regardless of the system
- The same diameter as the soil or waste stack
Correct answer: Half the diameter of the pipe it serves
A relief vent must be at least half the diameter of the pipe it serves, ensuring it can equalize pressure effectively in the drainage system.
Question 5: What does the Code require for piping that passes through a concrete floor slab?
- Direct encasement in concrete is acceptable
- A sleeve or casing must be provided to allow pipe movement (Correct answer)
- Insulation wrap is optional
- Only PVC pipe may penetrate concrete
Correct answer: A sleeve or casing must be provided to allow pipe movement
The Code requires a sleeve or casing around piping passing through concrete slabs to allow for differential movement and to protect the pipe from damage during concrete curing and structural settlement.
Question 6: According to the Code, what is the maximum number of water closets that can be connected to a 3-inch horizontal branch?
- 1
- 2
- 3 (Correct answer)
- 4
Correct answer: 3
A 3-inch horizontal branch can serve a maximum of 3 water closets, as each water closet contributes a significant fixture unit load and the branch has a limited capacity.
306A National Plumbing Code of Canada 6
What does the Code define as a 'wet vent'?