If you have a fairly new home, your hot water heater might already have a thermal expansion tank on it, since one is usually required by local building codes. If your hot water heater and plumbing are old, there may not be a tank present. However, you may want a plumber to add one for safety reasons. Here's the purpose of a thermal expansion tank and how a plumber installs one.

The Purpose Of A Thermal Expansion Tank

One of these tanks is installed near a water heater because of the principle that water expands when it's heated. Once the cool water in your heater gets hot, the water expands, and the pressure inside the tank increases. If the pressure gets too high, the tank could rupture if the relief valve isn't working. Constant pressure on the tank could cause the tank to wear out much quicker or leak.

To solve these problems, a plumber can install a small expansion tank near the water heater. When the water expands, it overflows in the expansion tank rather than exert pressure on the water heater.

A Thermal Pressure Tank May Be Required

If you're getting a new water heater, a thermal pressure tank may be required by local codes as a safety measure. The manufacturer of the water heater may also require an expansion tank to keep the warranty valid. If you add a backflow preventer device to your plumbing, you also want to add a thermal pressure tank. That's because a backflow preventer turns your plumbing into a closed system and there is nowhere for excess pressure to go without an expansion tank installed.

Besides being against local codes, operating a water heater with a backflow preventer in place could create dangerous pressure in the water heater or pipes that shorten the life of your plumbing. A tankless water heater and a home with an open plumbing system, such as one without a backflow preventer, would probably not need an expansion tank since pressure doesn't build up in the plumbing.

Where An Expansion Tank Is Installed

A thermal expansion tank is usually installed near your water heater. If you're retrofitting an old water heater, it may be difficult to squeeze the tank in an existing space, but your plumber will place the tank as close to the heater as possible so the tank can be monitored for leaks. The tank is usually put in a plumbing line above the heater with a T-adapter. If space is tight, the plumber may need to install a new pipe and additional connections to get the expansion tank in place.

If you're buying a new water heater and tank together, the expansion tank might have a shorter life than the water heater. It's important to check the tank regularly for leaks and other problems and have it replaced if it isn't working properly. The expansion tank is independent of the water heater and can be replaced without having to replace the heater.

For more information on how an expansion tank can help you, talk to your local plumbing service.