Friday, February 19th, 2016

Water Heater Science: Expansion Tanks

Every 6th grade science geek learns that upon freezing, water expands. But did you realize water also expands upon heating? It’s a property known as “thermal expansion,” which means that as water is heated, the water molecules speed up and require more space in which to roam. In a 40 gallon water heater tank, thermal expansion can create as much as a full gallon of additional water, by volume. The extra volume seeks to flow outward (as water likes to do).

Enter: Expansion tanks, small-ish steel cylinders that resemble 1 gallon water coolers and manage the expanded water so it doesn’t create plumbing problems. Typically, an expansion tank is connected to the cold water line that feeds your water heater. The tank contains an air valve, a rubber diaphragm and two inner chambers: one that fills water and one that holds air.

Expansion Water- Proper Placement Required
You may recall our recent blog on backflow prevention valves. Expansion water from your hot water tank is a good example of backflow– as the heated water expands, it will attempt to flow backwards into the city water lines. Fortunately, check valves at the meters (usually installed by the city) prevent such backflow. Unfortunately, the thermally expanded – hot, excited molecules with no place to go – water can create a build-up of pressure in your hot water tank.

High Water Tank Pressures = Trouble Ahead
Water heaters are built to withstand a certain amount of pressure, but excessive thermal expansion can create major headaches for homeowners. The pressure build-up can create leaks throughout your system or in the tank itself. By installing an expansion tank, a reservoir is added that provides an area for the expanded water to go until the water cools down or is used up. Expansion tanks allow your water heater to maintain a constant, safe pressure.

Learn More via YouTube
The “Handy Guys Podcast” ( offers a quick tutorial on expansion tanks, and several noteworthy bits of feedback from viewers.

Water You Waiting For? If you’re experiencing leaks around your hot water tank or are concerned about water heater pressure buildup, it’s possible an expansion tank might be a good option. The professionals at Allied Reddi Rooter can put your hot water into a tank containment program and potentially extend the life of your water heater. Call at 513-396-5300 or Contact  Ray today for a free quote or more information.  We always come highly recommended and have earned an A+ rating from the Better Business Bureau for our expert quality of service.