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Plumber Red Seal · Question

A plumber is roughing-in the drainage for a new bathroom containing a water closet, a lavatory, and a shower. According to the National Plumbing Code of Canada (NPC), what is the minimum total drainage fixture unit (DFU) load for this standard bathroom group?

For a standard bathroom group consisting of a water closet (3-4 DFU), lavatory (1 DFU), and shower (2 DFU), the minimum total DFU load according to the NPC is 6

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Question: A plumber is roughing-in the drainage for a new bathroom containing a water closet, a lavatory, and a shower. According to the National Plumbing Code of Canada (NPC), what is the minimum total drainage fixture unit (DFU) load for this standard bathroom group?

Answer options:

  • 4 DFU
  • 5 DFU ✅ 6 DFU
  • 8 DFU

Correct answer: 6 DFU

Explanation: For a standard bathroom group consisting of a water closet (3-4 DFU), lavatory (1 DFU), and shower (2 DFU), the minimum total DFU load according to the NPC is 6 drainage fixture units (e.g., 3 DFU for water closet + 1 DFU for lavatory + 2 DFU for shower = 6 DFU). This value is used for sizing the common drain pipe serving these fixtures. Other options are too low or too high for a standard residential bathroom group.

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