Air Release Valves, or Air Relief Valve function to release air pockets that collect at each high point of a full pressured pipeline. An air release valve can open against internal pressure, because the internal lever mechanism multiplies the float force to be greater than the internal pressure. This greater force opens the orifice whenever air pockets collect in the valve. Air Release Valves are essential for pipeline efficiency and water hammer protection.

Air release valves are installed at the highest points in a pipeline where air naturally collects. Air bubbles enter the valve and displace the liquid inside, lowering the liquid level. When the level drops to where it no longer buoys the float, the float drops.

Air valve used to release this free air is known as an air release valve. The second function of an air valve is to admit air into the system when the internal pressure of the pipeline drops below atmospheric pressures.