306A National Plumbing Code of Canada 3 — Questions and Answers
Question 1: According to the Code, what is the maximum interval between cleanout access points on a horizontal drainage pipe?
- 5 m
- 10 m
- 15 m (Correct answer)
- 20 m
Correct answer: 15 m
Cleanouts must be installed at intervals not exceeding 15 m on horizontal drainage runs to allow access for clearing blockages with standard drain-cleaning equipment.
Question 2: What test pressure is required for a DWV system rough-in test using water according to the Code?
- A column of water at least 1.5 m high
- A column of water at least 3 m high or 30 kPa (Correct answer)
- A column of water at least 5 m high
- 50 kPa air pressure
Correct answer: A column of water at least 3 m high or 30 kPa
The Code requires a water test of at least 3 m head (approximately 30 kPa) held for 15 minutes to verify the integrity of all joints and connections in the DWV system.
Question 3: What does the Code require for a cleanout at the base of every soil or waste stack?
- Cleanout is optional at the base of stacks
- A cleanout the same size as the stack, up to 4 inches (Correct answer)
- A 2-inch cleanout regardless of stack size
- A cleanout only if the stack is over 3 inches
Correct answer: A cleanout the same size as the stack, up to 4 inches
The Code requires a cleanout at the base of each stack that is the same size as the pipe, up to a maximum of 4 inches, to allow rodding access.
Question 4: According to the National Plumbing Code of Canada, what is the minimum clearance in front of a water closet?
- 300 mm
- 400 mm
- 450 mm
- 550 mm (Correct answer)
Correct answer: 550 mm
The Code requires a minimum clearance of 550 mm in front of a water closet to provide adequate user access and comfort.
Question 5: What minimum air gap is required between a faucet outlet and the flood level rim of a fixture?
- One pipe diameter
- Two pipe diameters or 25 mm, whichever is greater (Correct answer)
- 50 mm
- Three pipe diameters
Correct answer: Two pipe diameters or 25 mm, whichever is greater
The Code requires an air gap of at least two pipe diameters or 25 mm, whichever is greater, to prevent cross-connection and backflow contamination.
Question 6: What type of backflow preventer does the Code require for a high-hazard cross-connection?
- Dual check valve
- Atmospheric vacuum breaker
- Reduced pressure principle (RP) assembly (Correct answer)
- Hose bib vacuum breaker
Correct answer: Reduced pressure principle (RP) assembly
A reduced pressure principle (RP) backflow assembly is required for high-hazard cross-connections because it provides the highest level of protection with a relief valve that discharges to atmosphere if either check valve fails.
306A National Plumbing Code of Canada 3
According to the Code, what is the maximum interval between cleanout access points on a horizontal drainage pipe?