Venting

Air admittance valves (AAVs or Durgo valves or Studor Vents) are negative pressure-activated, one-way mechanical vents, used in a plumbing or drainage venting system to eliminate the need for conventional pipe venting and roof penetrations.

A discharge of wastewater 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.