A water heater is the fixture responsible for heating and storing the hot water flowing from every sink and shower in your home. A standard tank heater can stress your plumbing pipes when thermal expansion causes the hot water to take up more room in the tank.
Traditional tank-style water heaters and boilers for home heating systems could face problems from this pressure over time unless measures are taken to prevent damage. A water heater expansion tank is a way to preserve the life of plumbing systems.
What Is a Water Heater Expansion Tank?
A water heater expansion tank—or thermal expansion tank—is a small tank added to a water supply pipe. It acts as a safety device and minimizes the risk of pressure damage, bursts, and leaks in a home's plumbing system.
It activates when expanded hot water overflows from the main tank and pushes against an air cushion within the expansion tank, compressing the cushion and allowing water to flow in.
This alleviates the pressure of thermal expansion by giving the excess hot water a place to go. It also helps maintain consistent water temperature and pressure flowing through your home's taps.
Tip
Water heaters last about eight to 12 years. A thermal expansion tank reduces wear on the heater and can prevent a tank blowout, potentially extending its life.
Do I Need a Water Heater Expansion Tank?
Most modern-day water heaters are tankless, heating water on demand instead of keeping it stored, come with built-in thermal protection, or are installed within an open plumbing system. They don't usually need an expansion tank, but older models with traditional tanks and closed plumbing do.
What Is a Closed Plumbing System?
A closed plumbing system keeps water flowing one way, from your area's main supply, into your home instead of letting any flow back in the event of a pressure buildup. They are put in place to keep public water supplies clean and can be identified through check valves connecting the pipes and backflow prevention devices near your water meter or where pipes enter your home.
If you have an older water heater, there are a few telltale signs you may need to install an expansion tank. Look for drips and leaks from your faucets, fluctuating water pressure, loud noises, and mineral deposits around your water pipes' fittings.
These could all indicate stress on your plumbing system or pressure needing to be regulated and released from your pipes more frequently than it should.
What Size Water Expansion Tank Do I Need?
It is essential to ensure that your new water expansion tank is large enough to relieve the pressure from your main heater. Most homes need between two and five gallons, but the exact size will depend on the size of your water heater tank, the water pressure, and the starting and ending water temperatures.
- Start by checking your tank size using the sticker on your water heater.
- Next, test your home's water pressure with a water pressure gauge.
- Finally, use a thermometer to check the temperature of your taps' cold and hot water.
Once you have all the numbers you need, input the information into an expansion tank size calculator offered by brands Amtrol or Watts.
Water Heater Expansion Tank Costs
The price of a 2-4.4 water heater expansion tank on its own ranges from $40 to $200, and the cost of labor can fall anywhere between $50 and $150, depending on your area and the location and accessibility of your water heater tank.
When to Replace a Water Heater Expansion Tank
A water heater expansion tank typically lasts five to ten years. If you notice dripping water, mineral deposits on your pipes, decreased water pressure, or a change in water quality, it's best to check the health of your tank and consider a replacement.
Pros
Protects the health of your water heater and pipes
Extends the life of your plumbing system's parts
Prevents stagnant water
Prevents bursts, leaks, and pressure buildup
Helps your main tank to run more efficiently
Cons
Requires more space
Small issues can impact your home's entire water supply
Are complicated to install and require plumbing code knowledge
Can be high-maintenance and expensive
Can I Install a Water Heater Expansion Tank Myself?
Installing a water heater expansion tank requires knowledge of local plumbing codes, working with very hot and high-pressure systems, and potentially cutting your home's water pipes. It's highly recommended that you call a professional for this job to ensure your home's water supply stays working correctly and protects against water damage.
However, if you are confident in your plumbing skills and have a near-expert knowledge and experience, you can install a water heater expansion tank.
