Q - I am on a well and was wondering about my water heater. Two questions, what is an expansion tank and, being on a well, do I need one… -Rick in Grayson

A - A thermal expansion tank is a device that is hooked to a water heater to absorb excess water pressure that is caused by the heating of the water.

As you know, when something is heated, in this instance water, expansion occurs. It used to be that the expanding water simply pushed back into the cold water pipe and basically back into where it came from.

Now, with the invention of back-flow preventers and pressure reducing valves and the like, without an expansion tank, the expanded water would have nowhere to go, which adds pressure to your heater and that can be very hard on your water heater.

Now to your question of needing one if you are on a well.

Generally, the short answer is no, but only because most well pump systems already have one installed as a part of the pump.

Would it kill you to have one on your heater? No.

If you knew for a fact that your system did not have an expansion tank, then it would be a good idea to install one on your heater.

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