Oatey® Sure-Vent® 1.5 in. – 2 in. 160 Branch, 24 Stack DFU Air Admittance Valve with PVC Schedule 40 adapterThe Oatey Sure Vent 1. 5" 2" 160 Branch, 24 Stack DFU Air Admittance Valve with PVC Schedule 40 adapter is a one way valve designed to allow air into the plumbing drainage system when negative pressures develop in the piping system. Superior engineering along with stringent quality standards ensure unmatched performance. Oatey products have earned the trust of plumbing professionals for over 100 years. For use as a secondary vent PVC Schedule 40