When backflow prevention assemblies are installed, a closed system is created which locks in pressure into the downstream plumbing system. If there is equipment that can generate higher pressure than the incoming pressure, that excessive pressure can be trapped on the downside causing an over-pressurized condition on the piping. By the same token, when water is heated, the volume of water will expand, raising the downstream pressure, which the piping system may not be able to handle. In these situations, the use of relief valves and expansion control devices ensures that the fixtures, pipe, fittings, or backflow prevention assembly is not damaged. BAVCO carries several brands of expansion control devices, relief valves, hammer arrestors, and surge suppression devices to help solve your problem.