The automatic anti-siphon valve features a combination of an inline forward flow valve and an atmospheric vacuum breaker which prevents water flowing from the irrigation system back into the culinary system. This type of valve is most common in California. In other states it is common for a single backflow prevention device to protect the entire system at the mainline point of connection. To function properly, an anti-siphon valve should be installed at least 6 in. above the highest head in the zone which it controls. This typically requires the anti-siphon valve to be installed above-ground on risers. The atmospheric vacuum breaker features a reliable poppet design which closes when the valve shuts off. The automatic valve features a 24 VAC solenoid, manual actuation lever, and flow control. An internal scrubber filter helps keep the valve clog-free. The solenoid features nickel-plated copper wire and is compatible with all major brands of 24 VAC irrigation controllers. We recommend B-hyve controllers for optimum water conservation and PVC-Lock fittings for fast, glue-free installation. For outdoor irrigation use with cold water only.