Pressure Vacuum Breaker (PVB)
A Pressure Vacuum Breaker (PVB) protects your potable water supply from back-siphonage - water flowing backward due to a drop in supply pressure - using a spring-loaded check valve and air inlet valve that opens to break the vacuum if pressure drops. Unlike a DCVA, a PVB must be installed above the highest sprinkler head in the system to function correctly, which affects where it can be placed in a layout. Shop commercial-grade PVB assemblies and repair kits from Zurn Wilkins and FEBCO to keep your system protected and code-compliant.
Pressure Vacuum Breaker (PVB)
Backflow happens two different ways, and a PVB is specifically designed to stop one of them: back-siphonage, where a drop in the supply line's pressure — from a water main break, heavy demand elsewhere in the system, or a pump shutting off — creates a vacuum effect that can pull water backward out of the irrigation system and into the potable supply. A PVB uses a spring-loaded check valve to stop the backward flow, paired with an air inlet valve that opens automatically to break the vacuum the moment pressure drops, preventing the siphoning effect before it can pull water in the wrong direction.
The air inlet valve is also what makes installation height non-negotiable for a PVB: it has to sit above the highest sprinkler head in the system, typically by a minimum clearance specified by the manufacturer and local code, so that if the valve does open, water drains out through the air inlet rather than back into the irrigation line. This is the main practical difference from a Double Check Valve Assembly (DCVA), which doesn't have this height requirement and can be installed at grade.
A PVB protects against back-siphonage specifically, but not against back-pressure — a separate failure mode where pressure in the irrigation system itself exceeds supply pressure, which would require the added protection of a Reduced Pressure Zone Assembly (RPZ) instead. Confirming which failure mode your local code requires protection against is worth doing before choosing between the two.
Like any backflow assembly, a PVB typically needs periodic testing to confirm it's functioning correctly, and requirements vary by jurisdiction — check with your local water authority for specifics. If an existing PVB is failing a test or showing wear, Parts & Repair Kits cover common replacement components like poppet assemblies and air inlet parts without requiring a full assembly swap.
The Learn HUB has guides for understanding installation height requirements and choosing between PVB, DCVA, and RPZ assemblies.
