1" Anti-Siphon Jar Top Valve Rain Bird's Jar-Top anti-siphon valves combine the newest in Jar-Top technology with the reliability of anti-siphon protection. Jar-Top bonnet quickly screws on without using any tools. This allows you to easily access the diaphragm for effortless mainten ance and cleaning. Installed above ground to prevent back flow. Works with any standard sprinkler timer. Fail-safe design. External bleed to manually flush system of dirt and debris during installation and system start up. Heavy duty, professional design for a life time of trouble free operation. Flow control models regulate the flow of water to sprinklers to avoid misting. Vacuum breaker prevents backflow contamination to keep drinking water safe. Meets I.A.P.M.O. listing specifications.