Thermal expansion of water and / or water hammer down stream of the backflow presenter can cause pressure increases. Excessive pressure should be eliminated to avoid possible damage to the system and assembly.

Operation The Febco 765 PVB is designed to be installed to provide protection against backsiphonage of toxic or non-toxic liquids. It consists of a spring loaded check valve which closes tightly when the pressure in the assembly drops below 1 PSI or when zero flow occurs, plus, an air relief valve that opens to break a siphon when the pressure in the assembly drops to 1 PSI.

The assembly shall include two resilient seated shut-offs and two resilient seated test cocks, considered integral to the assembly. Assemblies must be factory backflow tested. The check valve and air inlet valve must be constructed to allow in-line servicing of the assembly. The valve body shall be constructed of bronze. The check, poppet and bonnet assembly shall be constructed of engineered plastic to protect the valve body from damage in the event of freezing.

Typical Applications PVB - Pressure Vacuum Breaker assemblies are used to protect against health hazard and non health hazard backsiphonage conditions in industrial plants, cooling towers, laboratories, laundries, swimming pools and lawn sprinkler systems.

Typical Specifications Pressure Vacuum Breaker assemblies shall be installed to withstand pressure for long periods and to prevent backflow of contaminated water into the potable water system in backsiphonage conditions. The Pressure Vacuum Breaker assembly shall consist of a single spring loaded check valve which closes tightly when water flow through the assembly drops to 1 PSI.

The discharge pressure of the Febco 765 pressure vacuum breaker shall be maintained above 3.0 PSI on 1/2 in though 1 1/4 in sizes and 5.0 PSI on 1 1/2in and 2 in sizes to insure seating of the spring loaded air inlet poppet.

Installation Specifications Febco 765 Pressure Vacuum Breaker assemblies should be installed at least 12 inches above the highest piping outlet and downstream of the assembly to preclude backpressure. In a sprinkler system that means the Febco 765 Pressure Vacuum Breaker must be installed 12 inches above the highest head in the irrigation system.

Febco 765 PVB assemblies should be installed so they are easily accessible for maintenance, periodic testing, and where discharge will not be objectionable. They should be protected from freezing. If the assemblies are subject to freezing temperatures, the freeze protection procedures outlines in the service manual that is included with the Febco 765 Pressure Vacuum Breaker must be followed. Assemblies must not be installed where backpressure could occur.

Pressure Vacuum Breaker assemblies shall be installed a minimum of 12 inches above the highest downstream outlet, and the highest point in the downstream piping. The assembly shall be rated to 150 PSI working pressure and water temperature from 32 degrees F. to 140 degrees F. The assembly shall meet the specifications of the USC* approval.