Are standard Air/Vacuum Valves mounted on a Surge Check Unit. The Air/Vacuum Valve operates in the normal fashion allowing air to escape freely. The Surge Check is a normally open valve (spring loaded) so that air passes through unrestricted, but when water rushes into the Surge Check Unit the disc closes against the spring and reduces the rate of flow of water into the air valve by means of throttling holes in the disc. This ensures normal gentle closing of the Air/Vacuum Valve and minimizes surges when the valve closes. As soon as the Air/Vacuum Valve is closed, the pressure on both sides of the surge Valve disc equalizes and the disc automatically returns to its open position. This means an Air/Vacuum Valve can open at any time the water level drops and line pressure approaches atmospheric and immediately have full re-entry flow of air into the pipe line before a vacuum can form. Ratings 125# thru 900# class.
Slow Closing Air/Vacuum Valves (AVS) Specifications
3 – 36″