Water Worker Amtrol Steel Electric or Gas Water Heater Expansion Tank 15 in. H X 11.5 in. W

Thermal / hot water heater expansion tanks prevent hot water from back flowing into cold water line or from escaping through the pressure relief valve and onto the floor. Prevents constant fluctuations in water pressure that damage the heater and associated piping. National plumbing code mandates installation when a backflow preventer is present.