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Plumber Red Seal · Question

A plumber is installing a new drainage system for a residential building. According to the National Plumbing Code of Canada (NPC), what is the minimum required slope for a 75 mm horizontal drainage pipe?

The National Plumbing Code of Canada specifies a minimum slope of 1 in 50 for horizontal drainage pipes 75 mm in diameter or less. A shallower slope like 1 in 1

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Question: A plumber is installing a new drainage system for a residential building. According to the National Plumbing Code of Canada (NPC), what is the minimum required slope for a 75 mm horizontal drainage pipe?

Answer options:

  • 1 in 100 ✅ 1 in 50
  • 1 in 25
  • 1 in 15

Correct answer: 1 in 50

Explanation: The National Plumbing Code of Canada specifies a minimum slope of 1 in 50 for horizontal drainage pipes 75 mm in diameter or less. A shallower slope like 1 in 100 would not provide sufficient velocity to scour the pipe, leading to potential blockages.

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