Watts Series 800M4QT Anti-Siphon Pressure Vacuum Breakers prevent the reverse flow of polluted water from entering into the potable water supply due to backsiphonage. It consists of bronze body construction, silicone rubber check valve disc, plastic check valve seat, stainless steel springs, a bonnet with silicone rubber O-ring seal, a lightweight plastic disc float, tee handle or lever handle shutoffs, and test cocks for winterization draining. Watts Series 800M4QT is ideal in health hazard continuous pressure applications such as irrigation systems and industrial process water systems where the water enters the equipment at or below its flood rim. Maximum Pressure:150psi (10.3 bar), Minimum Pressure: 15psi (55kPa)