Alternative Venting for Drain Pipes

Written by steve sloane
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Alternative Venting for Drain Pipes
AAVs remove the requirement for roof vent stacks. (Jupiterimages/BananaStock/Getty Images)

Traditional sewer lines require a vent pipe to run through the wall cavity up through the roof, allowing sewer gases to escape and fresh air to enter the sewer line. Where building codes permit, air admittance valves (AAVs) are installed instead of the vent.

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AAVs are one-way pressure activated vents. When water flows through the sewer line, the AAV opens and releases the air vacuum. This allows air to enter the sewer line so proper drainage can occur. At all other times, the AAV remains closed so no sewer gas can escape.


As less air vents need to be installed to sewer lines, sewer/vent installation costs are lowered through less time being required for installation, as well as less materials. Long-term maintenance issues associated with roof vent stacks are also alleviated.


AAVs are generally made of polyvinyl chloride (PVC) plastic, with ethylene propylene diene monomer (EPDM) rubber valve diaphragms included in the AAV structure. The valves can fit standard household diameter sewer pipes ranging from 1 1/4 inches to 4 inches and are cemented into place like regular sewer-vent lines. Each AAV is guaranteed to open at least 500,000 times, which equates to about 30 years of use.

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