When liquid heats up, its volume expands. When it comes to your water heaters, when a full tank of water heats up, it may need more room. But what if you don’t have the room in your tank?
This extra water volume can cause stress on other parts of the plumbing system. Extra water can result in broken pipes, leaky taps, relief-line leaks, a damaged or leaking water heater. There are even more serious safety concerns such as a bulging or ruptured tank. (WARNING: if you notice a bulge or rupture in your tank, it needs to be replaced immediately!) Most plumbing codes require residential and commercial plumbing systems to be able to accommodate water heater thermal expansion.
Many water tanks have a check valve designed to keep water expansion from being pushed back into the city water system. However, if your system doesn’t have an expansion or a check valve (and many don’t), the water pressure has nowhere to go. This just puts stress on the water heater tank itself and the surrounding pipes.
If this is the case, replacing your water heater won’t do much good because the changing pressure will keep adding stress to your plumbing system. The most effective solution here is to install a water expansion tank. This will give the tank the extra room it needs for when heated water expands.
If you have a closed plumbing system or your tank has already experienced thermal expansion damage, you should also install an expansion tank. What’s a closed plumbing system? It’s a water system that only has a one-way valve (think backflow valve, check valve or pressure-reducing valve). Because it’s only a one-way valve, any extra water pressure from thermal expansion will cause more damage because it can’t be pushed back into the city water supply. An open system on the other hand will push expanding water back into the city water supply.
Expansion tanks can cost anywhere from $40 to $200 depending on the size you purchase. Most homes have a 40-50 gallon water heater, so a simple 2-gallon tank will work. The tank is quite easy to install with a normal 3/4” threaded connection. A tee fitting will have to be installed above the water heater if one is not there already.