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Plumber Red Seal · Question

A plumber is installing a new bathroom group consisting of a lavatory, a water closet, and a bathtub. The developed length of the trap arm for the lavatory is 1.8 metres. According to the National Plumbing Code of Canada, what is the minimum required diameter for this lavatory trap arm?

According to the National Plumbing Code of Canada, a 32 mm trap arm has a maximum developed length of 1.2 metres. For a developed length of 1.8 metres, the next

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Question: A plumber is installing a new bathroom group consisting of a lavatory, a water closet, and a bathtub. The developed length of the trap arm for the lavatory is 1.8 metres. According to the National Plumbing Code of Canada, what is the minimum required diameter for this lavatory trap arm?

Answer options:

  • 32 mm
  • 38 mm ✅ 40 mm
  • 50 mm

Correct answer: 40 mm

Explanation: According to the National Plumbing Code of Canada, a 32 mm trap arm has a maximum developed length of 1.2 metres. For a developed length of 1.8 metres, the next size up, 40 mm, is required. A 38 mm pipe is not a standard size for trap arms, and 50 mm would be oversized for a lavatory trap arm.

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