20302 Maxi-Vent 3-Inch to 4-Inch Air Admittance Valve$$Plumbing & HVAC

Allow air to enter DWV systems to equalize pressure when water drains out of the system; eliminate the need for costly roof penetrations and vent piping. Vents up to 500 DFUs on a stack. For use with: Venting Single Fixture, Individual Branch, Circuit Vent Or Stack Type Application Up To 500 DFU. Material of Construction: ABS Plastic. Standards: ASSE Performance Standard 10510 And 1051, NES-592, NSF Standard 14, IAPMO, File No C-3803, ITS Intertek Testing Services.