Pressure Vacuum Breaker - Irrigation Backflow Device

A pressure vacuum breaker is a backflow prevention device that stops contaminated water from being siphoned back into the potable water supply.

What It Is

A pressure vacuum breaker, often called a PVB, protects irrigation and other outdoor water systems from backsiphonage. It uses a spring-loaded check valve and an air inlet valve so that if supply pressure drops, air enters the device and prevents dirty water from being pulled backward into the drinking water line.

It protects against backsiphonage only, not all forms of backpressure. That distinction matters when selecting the correct backflow device for a sprinkler or specialty water system.

Types

Most residential examples are bronze pressure vacuum breakers installed above grade with test cocks and shutoff valves. Spill-resistant pressure vacuum breakers are a related variation used where nuisance discharge is a concern.

Where It Is Used

Pressure vacuum breakers are commonly used on lawn irrigation systems, hose-fed chemical systems, and some outdoor water distribution setups. They are typically installed above the highest downstream sprinkler head and remain accessible for testing and winterization.

How to Identify One

Look for a brass assembly on the irrigation supply line with shutoff valves, test ports, and a bonneted top section above ground. It is usually located near the point where the sprinkler line branches from the house water supply.

Replacement

Replace a pressure vacuum breaker when it leaks from the bonnet, fails a backflow test, freezes and cracks, or will not hold pressure after rebuilding. Many units can be rebuilt with internal kits, but a cracked body usually means full replacement.

Pressure Vacuum Breaker — FAQ

Is a pressure vacuum breaker the same as a backflow preventer?

It is a type of backflow preventer, but not the only kind. A pressure vacuum breaker is specifically used to stop backsiphonage, not all possible backflow conditions.

Why does my pressure vacuum breaker leak when the sprinkler turns on?

A brief spit during startup can be normal, but steady leaking usually means worn internal parts, debris, or freeze damage. If it fails to seal after the zone pressurizes, it needs service.

Does a pressure vacuum breaker need to be above the sprinklers?

Yes. It is typically required to be installed above the highest downstream outlet so it can protect against backsiphonage correctly.

Can a homeowner replace a pressure vacuum breaker?

Some homeowners can replace an accessible unit, but irrigation backflow rules are often local and some areas require testing by a certified tester after the work. Freeze protection and proper height matter as much as the pipe connections.