Theory and Use of Air Valves

This article describes the theory and operation of air‐ release, air/vacuum, and combination air valves. All three prevent the accumulation of air at high points within a liquid distribution system. This is done by exhausting large volumes of air as the system is being filled and by releasing accumulated pockets of air when the system is operational and under pressure. Air/vacuum valves and combination air valves also prevent potentially destructive vacuums from forming by admitting air into the system during power outages, water column separation, or sudden ruptures of the pipeline. Additionally, these valves allow the system to be easily drained because air will reenter as needed.