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What is the minimum required slope for a 3-inch (75 mm) building drain according to the National Plumbing Code of Canada (NPC)?

The National Plumbing Code of Canada specifies a minimum slope of 1 unit in 50 units (1:50) for building drains 3 inches (75 mm) in diameter and larger to ensur

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Question: What is the minimum required slope for a 3-inch (75 mm) building drain according to the National Plumbing Code of Canada (NPC)?

Answer options: ✅ 1 unit in 50 units (1:50)

  • 1 unit in 100 units (1:100)
  • 1 unit in 25 units (1:25)
  • 1 unit in 200 units (1:200)

Correct answer: 1 unit in 50 units (1:50)

Explanation: The National Plumbing Code of Canada specifies a minimum slope of 1 unit in 50 units (1:50) for building drains 3 inches (75 mm) in diameter and larger to ensure adequate self-cleansing velocity. Smaller diameter pipes may require a steeper slope.

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