The air admittance valve is a one-way mechanical vent installed on a drain line. It opens under negative pressure to let room air into the pipe, preventing the water seal in the trap from being siphoned away. When the flow of wastewater stops, gravity and a spring close the valve tight to keep sewer gases from escaping into the building.
Heard on the job
We can't easily run a vent stack through this kitchen island, so just install an AAV under the sink.
Insider tip
Always install an AAV vertically and at least four inches above the trap weir, leaving it accessible for future replacement.
Also heard as
- air admittance valve
- Studor vent
- cheater vent