Expansion Tanks

Thermal expansion occurs when water is heated during non-use periods. The installation of a pressure reducing valve (PRV), check valve or backflow preventer "closes" the water system, leaving water with no room for expansion. Many local codes now require a closed system to prevent backflow into the water main.

Thermal expansion in a closed plumbing system can be damaging, dangerous and costly. Its effects include damage to water heater connections, damage to gas water heater flue tubes, damage to pumps serving washers and diswashers, leaking faucets, "weeping" of water through the water heater T&P safety valve, and noisy water hammer in the pipes.

Expansion tanks eliminate these problems by giving water a place to go when thermal expansion occurs. When a water heating cycle ends, or when any fixture is opened within the system, the impact of thermal expansion is reduced, and water drains out of the expansion tank back into the system.