Thermal expansion occurs when water is heated during non-use periods. It normally occurs when switching over from an open well system with a bladder style pressure tank to a closed system. A closed system is when the installation of a pressure reducing valve, check valve, or back flow preventer “closes” the system. This leaves the water with no room for expansion.
Thermal expansion in a closed plumbing system can be damaging, dangerous, and costly. The effects include damage to: water heater connections, gas water heater flue tubes, pumps serving clothes washers and dishwashers, temperature and pressure safety valves, leaking faucets, “weeping” of water through the water heater, and noisy water hammering in the pipes.
To eliminate these problems, we require the installation of an expansion tank. This gives the water a place to go when thermal expansion occurs. When a water heating cycle ends or any fixture is opened within the system, the impact of thermal expansion is reduced. The water drains out of the expansion tank back into the system. Expansion tanks are available through most plumbing suppliers and are easily installed.