During your next water heater replacement, you may notice that your plumber adds something new: a thermal expansion tank. But, you may ask, what is a thermal expansion tank? Why do I need one? Today, we’re going to explain the reasons and how a thermal expansion tank can help protect the water supply and your plumbing system.
Building codes
Cities are now beginning to require a thermal expansion tank on water heaters, and for an excellent reason: hot water expands. You may think that because there is a pressure relief valve, that will solve the problem, but not so: now that backflow preventers are built into homes constructed after 2005, a thermal expansion tank might prevent damage to your plumbing.
Thermal expansion basics
As water heats in a water heater, it expands. Exactly how much it expands depends on how hot the water was when it entered the tank and how hot it gets. But, say it’s a 40-gallon tank filled with 90-degree water that is then heated to 140 degrees. That 40 gallons of water will expand by almost half a gallon. That water will flow into a shower or washer, or whatever hot water appliance is running. However, if all hot water-using appliances are turned off, the extra hot water used to back up into the freshwater main. But, because homes now come with a backflow prevention device, water can’t seep back into the freshwater supply—an option no one really wants.
If a hot water tank doesn’t have a thermal expansion tank, the extra water created by heating will put pressure on the system. It might cause something simple to repair, like a leaky faucet. Or, it might damage your water heater or a plumbing joint in the wall.
Pressure testing
The thermal expansion tank should be tested once a year. We can do that during a service visit, or you can do it yourself if you’re handy with DIY projects. But, even if you aren’t, you can check the tank to see if the relief valve is leaking, or if the entire tank is uniformly warm: the lower half of the tank should be warm, but the upper half should feel cool.
If you do not have a thermal expansion tank, you may be replacing your water heater more often than necessary, or having other plumbing problems related to thermal pressure in the lines. A thermal expansion tank can solve pressure problems and keep your plumbing system free of unnecessary damage.
SW plumbing & gas offers prompt, professional residential and commercial plumbing installation, repair, and drain services in the Auckland area. Call 021-460-487.
