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Plumber Red Seal · Question

When installing an island fixture vent (loop vent) for a kitchen sink, where must the top of the vent loop be located?

The top of the loop vent must extend above the flood level rim of the fixture it serves. This is a critical requirement to prevent waste from a clogged drain fr

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Question: When installing an island fixture vent (loop vent) for a kitchen sink, where must the top of the vent loop be located?

Answer options:

  • As high as possible within the cabinet, but below the sink
  • At the same elevation as the fixture's P-trap weir ✅ Above the flood level rim of the island sink
  • Below the finished floor level

Correct answer: Above the flood level rim of the island sink

Explanation: The top of the loop vent must extend above the flood level rim of the fixture it serves. This is a critical requirement to prevent waste from a clogged drain from flowing over the loop and into the vent portion of the pipe, which would render the vent ineffective.

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