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Plumber Red Seal · Question

When is a backwater valve mandatory for a sanitary building drain?

The NPC requires a backwater valve to be installed when a fixture is located below the level of the adjacent street or public sewer to prevent sewage from backi

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Question: When is a backwater valve mandatory for a sanitary building drain?

Answer options:

  • When the building has more than three storeys.
  • When the building drain is constructed of PVC. ✅ When the fixture drain is located below the level of the adjoining street.
  • When the total connected fixture unit load exceeds 500.

Correct answer: When the fixture drain is located below the level of the adjoining street.

Explanation: The NPC requires a backwater valve to be installed when a fixture is located below the level of the adjacent street or public sewer to prevent sewage from backing up into the building during a sewer surcharge event.

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