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Plumber Red Seal · Question

What is a fundamental requirement for installing air admittance valves (AAVs) within a building's drainage system?

Air admittance valves only allow air to enter the system, not exit. Therefore, the NPC requires that at least one main vent stack must extend to the atmosphere

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Question: What is a fundamental requirement for installing air admittance valves (AAVs) within a building's drainage system?

Answer options:

  • An AAV is installed on every fixture trap. ✅ The building must have at least one main vent stack extending to the open air.
  • AAVs must be installed below the flood level rim of the fixture they serve.
  • They can only be used on systems with a hydraulic load of less than 10 DFUs.

Correct answer: The building must have at least one main vent stack extending to the open air.

Explanation: Air admittance valves only allow air to enter the system, not exit. Therefore, the NPC requires that at least one main vent stack must extend to the atmosphere to relieve positive pressures within the drainage system.

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