306A National Plumbing Code of Canada 4 — Questions and Answers
Question 1: According to the Code, which material is NOT approved for use as a building sewer pipe?
- ABS
- PVC
- Cast iron
- Corrugated steel (Correct answer)
Correct answer: Corrugated steel
Corrugated steel is not an approved material for building sewers under the National Plumbing Code of Canada. Approved materials include ABS, PVC, cast iron, and vitrified clay.
Question 2: What is the minimum vent pipe size permitted by the Code?
- ¾ inch
- 1 inch
- 1¼ inch (Correct answer)
- 1½ inch
Correct answer: 1¼ inch
The National Plumbing Code of Canada specifies a minimum vent pipe size of 1¼ inch (32 mm) to ensure adequate air flow for trap seal protection.
Question 3: What does the Code require when a horizontal drain pipe changes direction by more than 45 degrees?
- No special requirements
- A cleanout must be provided at the change of direction (Correct answer)
- The pipe must increase in size by one increment
- A vent must be installed within 600 mm
Correct answer: A cleanout must be provided at the change of direction
The Code requires a cleanout at any point where a horizontal drainage pipe changes direction by more than 45 degrees to allow maintenance access at potential blockage points.
Question 4: According to the Code, how high above the roof must a vent pipe extend when penetrating a roof?
- 75 mm
- 150 mm
- 300 mm minimum, but varies with snow load zone (Correct answer)
- 600 mm in all cases
Correct answer: 300 mm minimum, but varies with snow load zone
Vent pipes must extend at least 150 mm above the roof but in areas subject to snow loads, they must extend higher to remain clear of snow accumulation. Typical requirements range from 300 mm to 600 mm depending on local conditions.
Question 5: What is the fixture unit value assigned to a domestic kitchen sink by the Code?
- 1 fixture unit
- 1.5 fixture units
- 2 fixture units (Correct answer)
- 3 fixture units
Correct answer: 2 fixture units
A domestic kitchen sink is assigned 2 fixture units in the National Plumbing Code of Canada, reflecting its typical flow rate and drainage demand.
Question 6: According to the Code, what is the maximum fixture unit load on a 3-inch building drain at a slope of 1 in 50?
- 12 fixture units
- 27 fixture units (Correct answer)
- 42 fixture units
- 60 fixture units
Correct answer: 27 fixture units
A 3-inch building drain at a 1 in 50 slope is rated for a maximum of 27 fixture units according to the drainage sizing tables in the Code.
306A National Plumbing Code of Canada 4
According to the Code, which material is NOT approved for use as a building sewer pipe?