What is a THERMAL EXPANSION TANK, and do I need one?
When water is heated it expands. If your system is “open” then water can backflow into the water main and this “extra” expanded water simply flows out of your home back out your cold pipe. Increasingly, home plumbing systems are being closed off and backflow prevention valves are being placed between homes and the water main. This is done for a variety of reasons. For example, increasingly valves are placed between homes and water mains to protect plumbing systems from inlet water pressure. Water pressure is increasing in many cases in order to meet the demands of more densely populated areas. If your system is “closed”, then this means when you heat your water and it expands, this increased volume has no where to go. As water is not a very compressible material, this causes sudden increases in water pressure which can damage your water heater and your other appliances. A thermal expansion tank is a pressurized tank that sits on your cold line – typically near or on your water heater.
