This professional grade anti-siphon valve replaces Rain Bird and other irrigation valves installed above ground with 3/4 in. female threaded inlet and outlet. It can be used with any 24 volt AC irrigation timer. Its unique reverse-flow design helps prevent flooding in the event of internal diaphragm failure, keeping the valve closed and saving water. Anti-Siphon valves should always be installed at least 6 inches above the highest head on the valve line, and should never have another valve installed further down the line from the main valve. After installation and before startup, always the flush system of dirt and debris manually using the valve's external bleed screw. Equipped with the additional advantage of adjustable flow control, this model helps prevent wasteful misting when water pressure is too high. A top mounted, easy turn flow control knob allows you to optimize flow to the zone, permitting sprinklers to water at their most efficient rate for more uniform coverage. This valve can be applied with all types of watering devices including Rain Bird spray heads (1800, 600), and rotors (22SA, 32SA, 42SA+, 52SA, LG3 and AG5) as well as Drip zones when properly installed together with a pressure regulator and filter.