A PVB has a spring-loaded check valve and an air inlet under a plastic or metal canopy. When pressure is normal, the poppet seals the air inlet. When pressure drops, the poppet lifts and lets air in so water cannot be siphoned back.
Because it sits outdoors in full sun on many Fullerton yards, the canopy, bonnet and rubber parts take a beating. Owners usually notice the problem when the device sprays during watering or water seeps from under the cap.
Symptoms and likely causes
| Symptom | Likely cause | Typical fix |
|---|---|---|
| Brief spit when a zone starts | Poppet seating as pressure builds; often normal | Watch it; test if it continues |
| Constant spray from under the canopy | Worn or debris-fouled poppet seal | Clean or replace poppet assembly, retest |
| Leak around the bonnet | Bonnet O-ring or cracked bonnet | Replace seal or bonnet, retest |
| Cracked body or canopy | Sun, impact or very rare freezing | Replace damaged part or whole device |
| Weak sprinkler pressure | Partly closed shutoff or debris in the check | Open shutoffs fully, clean check, retest |
| Leaking test cock | Worn test cock or missing cap | Replace test cock, retest |
Safe checks before calling a tester
Check the shutoff handles
Both ball valve handles should be in line with the pipe when open. A half-closed valve causes low pressure.
Look for physical damage
Cracks, a loose canopy or a bent riser often explain leaks.
Note when it leaks
Leaks only at start-up are different from a constant leak.
Shut off if it is spraying hard
Close the upstream shutoff or the irrigation supply valve until it can be repaired.
Installation basics
- Height
- Typically installed at least 12 inches above the highest sprinkler head it serves; check with the city
- Orientation
- Upright, with the canopy on top
- Protects against
- Backsiphonage only, not backpressure
- Testable
- Yes, with test cocks and two shutoffs
Ask before approving a repair
- Is it the poppet, the check, a seal or the body that failed?
- Is a rebuild kit available for this brand and size?
- Is the device installed high enough for the yard as it is now?
- Will you retest and file the report after the repair?
Common questions
Can a PVB protect a system with a pump?
A PVB does not protect against backpressure. If there is a booster pump or other pressure source, ask the supplier what device is required.
Why does my PVB only leak at night?
Many controllers water early in the morning, when supply pressure can also be different. The leak likely appears whenever zones start and stop.
Is a PVB the same as an anti-siphon valve?
No. Anti-siphon valves combine a sprinkler valve with an atmospheric vacuum breaker, which is not testable. A PVB is a separate testable device.
General information for Fullerton, not a quote or professional advice. In an emergency, call 911.