A water heater expansion tank

Does My Water Heater Need an Expansion Tank?

Water expands when heated. This is called thermal expansion. Because your water heater can hold only so many gallons, all that extra water has to go somewhere. An expansion tank absorbs excess pressure, alleviating strain on your water heater and plumbing system.

How an Expansion Tank Works

An expansion tank connects to the cold water line coming into the water heater tank. It’s divided into two parts by a rubber baffle. Thermal expansion forces water into the bladder, pushing the baffle down into a chamber filled with compressed air, absorbing the pressure. Not only does this alleviate strain on the tank, but it’s also sparing your plumbing joints, toilet valves, and solenoid valves on your washing machine and dishwasher from damage.

Signs You Need an Expansion Tank

Your home is on a closed-loop system: On an open-loop system, excess water created by thermal expansion would flow back to the main water line. If your home is on a closed-loop system, all that extra pressure will cause the tank to expand and contract, which will lead to premature failure of the unit. If your main water shutoff valve has a pressure regulator, a backflow prevention device, a sort of bell-shaped mechanism, then your home is on a closed-loop system.

The TPR valve leaks: Your water heater’s temperature/pressure relief valve (TPR) is a safety mechanism that activates when -- you guessed it -- the temperature or pressure exceeds unsafe levels. It will discharge a jet of hot water to regulate the pressure. It’s a mess but it’s better than the alternative: an exploding water heater. If the TPR valve frequently trips, you may need an expansion tank.

Water Heater Tank Maintenance

The bottom half of the expansion tank is filled with compressed air, generally somewhere around 50 and 60 pounds per square inch (PSI). The tank may lose some pressure over time.

The tank has a Schrader valve, the same type of valve you’d find on a bicycle tire. Check it with a pressure gauge annually to see if it’s sufficiently charged. If it’s less than 50psi, you can pressurize it with a bicycle pump.

Bottom line: The water heater installation pros in Gilbert are happy to assess the condition of your water heater to determine if it could benefit from an expansion tank. Consider scheduling your appointment with Plumbing & A/C Medic by calling (602) 975-2306.