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Plumber Red Seal · Question

A plumbing apprentice is installing a new kitchen sink drain. The local plumbing code, based on the National Plumbing Code of Canada, specifies a maximum length for a horizontal trap arm. If the trap arm is connected to a vertical stack, what is the maximum developed length permitted for a 38 mm (1 1/2 inch) trap arm?

According to NPC Table 2.5.7.3. (or similar provincial tables for trap arm lengths), the maximum developed length for a 38 mm (1 1/2 inch) trap arm is 1.0 m. Ex

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Question: A plumbing apprentice is installing a new kitchen sink drain. The local plumbing code, based on the National Plumbing Code of Canada, specifies a maximum length for a horizontal trap arm. If the trap arm is connected to a vertical stack, what is the maximum developed length permitted for a 38 mm (1 1/2 inch) trap arm?

Answer options: ✅ 1.0 m

  • 1.2 m
  • 1.5 m
  • 2.0 m

Correct answer: 1.0 m

Explanation: According to NPC Table 2.5.7.3. (or similar provincial tables for trap arm lengths), the maximum developed length for a 38 mm (1 1/2 inch) trap arm is 1.0 m. Exceeding this length can compromise the trap's seal due to siphonage or backpressure.

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