Thermal Expansion

Once we install a backflow preventer on your water service line, water will be unable to flow back into the public water supply. The backflow preventer creates an isolated or closed plumbing system. For some homeowners, this could produce leaky faucets or set off the temperature and pressure relief valve on hot water heaters.

Why does this happen? The culprit is Thermal Expansion. Before the backflow preventer was in place, water was forced back out to our public water supply by means of the hot water heater. Let me explain, as water was heated, it increased in volume and pressure forcing it back out to the water main, thus we get the term "thermal expansion." Once a backflow preventer is installed, the water can no longer expand in this direction and a plumbing system that is not up to current code could experience the conditions mentioned above. If your plumbing system is faulty, it could fail once the system is closed. For example, if thermal expansion exerted itself and the hot water heater relief valve was stuck, the hot water heater could develop a leak.

Who is Affected ? Most customers will never experience these problems. For the majority of those that do, simply lowering the temperature setting of the hot water tank to 115-125 degrees (which is sufficient for most purposes) will eliminate the problem. However, we strongly encourage you to make sure your plumbing system is up to current building code standards. You should consult a certified plumber if you have any doubts about your plumbing's condition. A plumber may recommend the installation of a thermal expansion tank if you have a hot water heater or a pressure reducing valve if your water pressure exceeds 75 pounds per square inch (psi). The illustration above shows these devices installed in a typical setting. As an added note, these devices will pay for themselves by protecting your plumbing system and conserving water by helping to prevent failures of your plumbing fixtures.

The BCPSWD, through our backflow protection and other initiatives, strives to produce water of the highest quality and safety at a reasonable cost. With the installation of a backflow preventer, you can rest assured that you are helping to protect your health and welfare as well as that of your neighbors and the community at large.

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