Design Vogue

A pressure vacuum breaker (PVB) is a safety component of irrigation systems. It stops non-potable irrigation system water from flowing back to your home's drinking water supply.

Learn why a pressure vacuum breaker is essential, where to find it, and how to maintain it.

Why You Need a Pressure Vacuum Breaker

A pressure vacuum breaker prevents water contamination. Most local building codes require a backflow prevention device on water systems. 

Since there is usually only one water system in the home for drinking water and all household use, including irrigation, there is always the risk of cross-contamination from backflow.

Backflow can occur if there is a sudden drop in the water pressure in the home's main water supply. For example, if the city water is interrupted for any reason, this could result in negative pressure on the home's main supply. Though rare, negative pressure can cause the water to flow backward in the pipes.

Where to Find the Pressure Vacuum Breaker

A pressure vacuum breaker is installed close to the water source before entering the sprinkler valves. It must be installed above the highest point in the system, usually the highest sprinkler head or the highest slope in the yard.

Most sprinkler systems have a PVB located outdoors, but sometimes it will be found indoors.

How a Pressure Vacuum Breaker Works

A pressure vacuum breaker consists of a check device or check valve and an air inlet vented to the atmosphere (open-air). The check valve allows water through and keeps the air inlet closed during normal conditions. 

When the air pressure exceeds the water pressure, the vented chamber opens and breaks the suction effect of the low pressure. This prevents the water from backflowing.

Pressure Vacuum Breaker Maintenance

Regular maintenance for a pressure vacuum breaker is minimal. The internal components may need replacement every five years. Check on the PVB whenever inspecting the irrigation system.

O-ring gaskets that seal against the inner walls of the breaker might become brittle and crack over time. The plastic poppet and bonnet can also wear out. When these components malfunction, this can cause water to pour out from under the cap.

• Periodically, check the breaker for leaks.
• Check sealing tape/plumber's putty at connection points for leaks.
• They might leak if sealing tape or plumber's putty connecting either side of the breakers is worn, incorrectly installed, or missing.
• Check the connections and replace the seals, if necessary.
• Inspect the o-ring gasket integrity.
• Drain in winter to prevent blowout; open valves halfway.
• Check the sprinkler controller to make sure that it is working.

Winterizing a Pressure Vacuum Breaker

The most important regular maintenance item is protecting the PVB from freezing during cold weather. Draining the PVB during a sprinkler blowout is critical for winterizing a sprinkler system.

Failing to drain a PVB can damage its internal parts by cracking or bursting the PVB, requiring replacement.

Once the sprinkler system is winterized, the valves on a PVB typically are opened halfway to allow air to escape if residual water inside the PVB freezes. Air will prevent pressure buildup that can damage the parts.

Repairs

The internal components of a pressure vacuum breaker can become damaged by freezing and through regular use over time. A clear sign that something is not working properly is leaking from under the bell or bonnet assembly of the valve. Repair kits are available from the manufacturer specific to each PVB model.

A standard repair consists of turning off the inlet and outlet ball valves then removing the bonnet assembly. Since the repair parts are installed in the reverse order, it is good to keep the components well organized as they are removed.

The repair parts are then installed, and the water supply is turned on (inlet water supply valve first). The local building code may dictate whether or not a homeowner is allowed to repair the backflow device. If a homeowner is permitted to repair the backflow device, an inspection of some sort is likely required.