This professional grade anti-siphon valve replaces Rain Bird and other irrigation valves installed above ground with ? 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. The Jar-Top bonnet quickly allows quick access to the diaphragm for easy maintenance. Anti-Siphon valves should always be installed at least 6" 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.