[rohrmann]

Another reason to install an accumulator/expansion tank is to keep water from leaking out of the TP valve on the water heater. There is a check valve on the city water connection, and when using hot water which turns on heat to bring the water heater back hot again, water will expand, and when it has no where to go, the TP valve will open to relieve the pressure because water can not go back out the hose like in a S/B house. This also happens when dry camping.