The Pressure Vacuum Breaker Assembly (PVBA) is an outgrowth of the atmospheric vacuum breaker and evolved in response to a need to have an atmospheric vacuum breaker that could be utilized under constant pressure and was testable. These assemblies may be used under constant pressure but do not protect against back-pressure conditions. The assembly must be at least 12 inches higher than any downstream piping.
A diagram of a Pressure Vacuum Breaker is illustrated below along with typical installation drawings:
