Specialty Products™ Air Admittance Valve, 1-1/2 to 2 in Nominal, -40 to 150 deg F, ABS Body, White

Air admittance valves (AAV) provide an acceptable means for ventilating a plumbing drainage system without venting through the roof or to open atmosphere. AAVs ensure that no sewer gases or liquids will enter the building through the valve. The AAV closes by gravity, sealing at zero-differential pressure and remains closed under positive internal pressure (back pressure). It opens under negative pressure to allow proper drainage to occur without siphoning of fixture traps.