Fixing a Leaking Anti-Siphon Valve
If you have an above-ground sprinkler valve that spits or leaks water out the top when the zone runs, it's likely an anti-siphon valve with a worn part. These common valves combine flow control with backflow protection, and they have a specific failure point. Here's how to fix a leaking anti-siphon valve.
What an anti-siphon valve does
An anti-siphon valve is a control valve with a built-in atmospheric vacuum breaker that prevents irrigation water from siphoning back into your drinking water. They're installed above ground, a few inches higher than the highest sprinkler head, which is why you can see them leaking.
Why it leaks from the top
Water spitting or weeping from the top bonnet when the zone runs usually means the poppet or float assembly in the vacuum breaker is worn or stuck. This rubber seal allows air in when the system is off but should seal against water when it runs. When it fails, water escapes from the top.
How to fix it
- Shut off the water to the valve.
- Unscrew the top cap of the anti-siphon (vacuum breaker) portion.
- Remove the poppet/float assembly and inspect the seal.
- Replace it with a matching repair kit for your valve model.
- Reassemble and test — the top leaking should stop.
If the lower control section leaks instead, the diaphragm likely needs replacing, similar to other valves.
When to replace
If the valve body is cracked or repair parts aren't available, replacing the valve is the move. Our irrigation team can repair or replace anti-siphon valves.
Frequently asked questions
Why does my anti-siphon valve squirt water from the top?
Usually a worn poppet or float seal in the vacuum-breaker section. A repair kit for that part typically fixes it.
Can I repair an anti-siphon valve myself?
Often yes — replacing the vacuum-breaker poppet or the diaphragm with a model-specific kit is a manageable DIY repair.
Arbol Roble has cared for Inland Empire landscapes since 1997, serving Rancho Cucamonga, Ontario, Fontana, Eastvale, Corona and Riverside. Request a free quote or browse our residential and commercial services.
About the Author
The Arbol Roble team are licensed landscaping and irrigation professionals (CSLB License #1077455) serving Rancho Cucamonga, Ontario, Fontana, Eastvale, Corona, Riverside, and the greater Inland Empire.