The purpose of Air Valve and Vent Inflow Preventer Assemblies is to allow the release and admission of high volumes of air through air valves and air vents in water distribution systems but prevent the entry of contaminated water when the air valve outlet becomes submerged from flooding or is the target of malicious tampering.

This assembly shall consist of a primary and a secondary chamber. Each chamber shall contain an independent float-operated closure member. The primary chamber is the lower chamber. The secondary or upper chamber is redundant and will close in the event the primary chamber fails to close.