Air Admittance Valves

What are Air Admittance Valves?

An air admittance valve is a small mechanical device that helps provide airflow for trap seals, without the need for additional stack vent piping out the roof. If an AAV is an acceptable option, they can prevent the need to cut holes in walls, ceilings, attics and roofs, thus saving much time and labor expense.

A discharge of waste water causes the AAV to open, releasing the vacuum and allowing air to enter plumbing vent pipe for proper drainage. Since AAVs will only function under negative pressure situations they are not suitable for all venting applications, such as venting a sump, where positive pressures are created when the sump fills.