DESCRIPTION:  A pressure vacuum breaker assembly consists of an independently operating internally loaded check valve and an independently operating loaded air inlet valve located on the discharge side of the check valve, with properly located resilient-seated shutoff valves attached at each end of the assembly.


     FUNCTION:  In a normal flow situation, which the internally loaded check valve remains open, the air inlet valve is closed. When a backsiphonage condition develops, the internally loaded check valve closes.  And, if this check is not fouled, it precludes the backsiphonage of water from the PVB body and downstream piping.  However, if the check valve is fouled, the air inlet opens with the cessation of normal flow and allows air to enter the supply pipe through the fouled check valve, thus, breaking the vacuum and not permitting backsiphonage from the downstream piping.


     APPLICATION:  The PVB is effective against backflow caused by back-siphonage only and should not be used if backpressure could develop in the downstream piping.   The PVB in normally used to isolate both pollutants and contaminants.  This assembly is not for use at a meter because of its inability to protect against backpressure conditions.  If used for health hazards, careful consideration must be given to the possibility of the assembly being circumvented.  Where such possibilities exist, area or premises isolation is necessary.