Reduced Pressure Backflow Assembly


Typical small RPBA

The RPBA is designed so that if one of the check valves leaks, the relief valve will discharge any possible contaminates to waste through the relief valve vent. A zone of reduced pressure is maintained in between the 2 check valves. If either check valve leaks, the pressure relief valve is to maintain a differential pressure between supply and the reduced pressure zone by discharging water to atmosphere, (waste), through the relief valve. Water occasionally discharging from the relief valve is not necessarily an indication that the assembly is malfunctioning. They will often “spit” water when pressure fluctuates. For this reason, as well as the possibility of the event of a backflow situation, or a failing assembly, the owner must make sure that there is an adequate drain with the proper air gap, to carry the discharge away. A check valve installed immediately upstream of the assembly will greatly reduce, and often eliminate this “nuisance spitting”. RPBA’s offer acceptable protection against the highest degree of health hazard backflow protection, but must be tested and maintained carefully to insure that they continue to operate as designed. RPBA’s provide protection in back siphonage and back pressure backflow events.

Before installing any backflow assembly, the owner should contact a state certified, licensed, bonded, and insured backflow assembly technician, such as those here at BATMASTER, 425-397-0275, to (1) make sure that you have a Washington State approved assembly, (2) know the installation requirements, and (3) to prevent costly mistakes.


It is wise to install a “RPBA with a bypass RBPA” in cases where a complete water outage is unacceptable to the customer such as hotels and hospitals where service interruption is to be avoided when possible. All BPA’s fail at some point and without the bypass BPA, a service interruption is inevitable.