Thermal Expansion Within the Plumbing System

Davidson Water, Inc. requires the installation of a backflow prevention device within your water meter box in order to protect the distribution system from potential cross connections or backflow from a customer. Such cross connections or backflow could result in pollution and/or contamination of the water system.

When a backflow preventer device is installed in your meter box, water from the building/house will be unable to flow back into the water system. The backflow preventer creates an isolated or closed plumbing system. For some homeowners, thermal expansion could produce leaky faucets or set off the relief valve on hot water heaters, or in some cases, other damage may occur. Thermal expansion occurs when your hot water heater heats the water, causing it to expand.

In order to control thermal expansion, simply lowering the temperature setting of the hot water tank to 115-125 degrees (which is sufficient for most purposes) might reduce the possibility of thermal expansion. A plumber may recommend the installation one of the following two types of products available to control thermal expansion:

Thermal expansion tank on your hot water heater. Layout shown below is for demonstration purposes only.

A toilet tank ball cock fill valve,anti-siphon backflow preventer and thermal expansion relief valve, all in a single assembly.

A pressure-reducing valve may also be required if your water pressure exceeds 70 pounds per square inch (psi).

Davidson Water, Inc. is dedicated to providing you with superior quality drinking water that exceeds federal standards. With the installation of a backflow preventer after your water meter, you can feel confident that we are protecting you and your family as well as your neighbors and community.

Part One:	Thermal Expansion
Part Two:	Frequently Asked Questions