Thermal expansion is a condition that exists whenever water is heated. The heated water cannot expand into the public water system because of the backflow device. Therefore, pressure may build up in your water heater tank and household plumbing. The resulting pressure buildup, or thermal expansion, usually causes the pressure relief valve (T&P valve) on your water heater to open and water is emitted from the drain piping. Under certain conditions, such as a failure of the T&P valve, or the thermal expansion tank, a water heater may rupture.

If you notice a discharge of water from your water heater or abnormally high water pressure when you first turn the water on, you may be experiencing thermal expansion. Current plumbing codes require the installation of thermal expansion relief devices in closed systems. Newer residences may already have a thermal expansion relief device installed whereas some older homes may not. If you are unsure if your water heater has a properly working thermal expansion tank or T&P valve, we suggest you discuss your concerns with a licensed plumber.

For more information, view this guide to thermal expansion.

If you have any questions, please call the City of Melbourne Utilities Operations office at (321) 608-5126.