How Does a Sprinkler System Vacuum Breaker Work?

Causes

• Back-siphonage occurs when water in a system enters a vacuum situation and a siphon action starts. The siphoning allows the contaminated water to co-mingle and mix with potable water. For example, back-siphonage occurs when pipes lose pressure due to the water being turned off. In addition, large water mains are in use due to pool filling in the area causing a vacuum. Water could be sucked in through a hose left in pond which then draws pond water into the potable source.

AVBs

• Atmospheric vacuum breakers (AVBs) attached to valves have a float raised to the top of the valve when water is pressurized sealing the valve from the atmosphere. When the valve is in the off position, the float drops down and seals the valve off from the potable source allowing air access to the downstream pipes breaking the vacuum. An AVB works well for homes and non-commercial applications.

PVBs

• Pressure vacuum breakers (PVBs) work with a check valve installed in the water flow with a chamber vented to the atmosphere. During normal operation, the spring loaded check valve is open and the vented chamber is closed. When a vacuum situation occurs, the check valve shuts closed, protecting the potable water and the vented chamber opens allowing air in and backflow out. A PVB is good for residential use.