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Plumber Red Seal · Question

According to the National Plumbing Code (NPC), when may an air admittance valve be used to vent a fixture?

Air admittance valves (AAVs) are generally restricted and permitted by the NPC primarily for island sinks or in situations where extending a vent to the outdoor

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Question: According to the National Plumbing Code (NPC), when may an air admittance valve be used to vent a fixture?

Answer options: ✅ Only when connecting to an existing system where a traditional vent is not possible.

  • On any new construction fixture group as a primary vent.
  • In a location that is subject to freezing temperatures.
  • To vent sump pits or Macerating toilet systems.

Correct answer: Only when connecting to an existing system where a traditional vent is not possible.

Explanation: Air admittance valves (AAVs) are generally restricted and permitted by the NPC primarily for island sinks or in situations where extending a vent to the outdoors is structurally impractical, especially in renovations.

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