A plumber is roughing in a new kitchen sink. The developed length of the trap arm connecting the sink trap to the branch drain is 1.5 metres. If the trap arm is 40 mm in diameter, will it comply with the National Plumbing Code of Canada?

Question: A plumber is roughing in a new kitchen sink. The developed length of the trap arm connecting the sink trap to the branch drain is 1.5 metres. If the trap arm is 40 mm in diameter, will it comply with the National Plumbing Code of Canada?

Answer options:

• Yes, because 40 mm is always sufficient for a kitchen sink.
• No, the maximum developed length for a 40 mm trap arm is 1.5 metres, so this is exactly at the limit. ✅ No, the maximum developed length for a 40 mm trap arm is 2.5 metres, so it is compliant.
• No, the maximum developed length for a 40 mm trap arm is 1.2 metres, so it is too long.

Correct answer: No, the maximum developed length for a 40 mm trap arm is 2.5 metres, so it is compliant.

Explanation: According to the National Plumbing Code of Canada, the maximum developed length for a 40 mm diameter trap arm is 2.5 metres. Therefore, a 1.5-metre trap arm is compliant. A 32 mm trap arm has a maximum developed length of 1.2 metres, and a 50 mm trap arm can extend further, but 40 mm is sufficient here.