How to Replace Your Water Heater Expansion Tank

water heater with attached expansion tank
  • 2-5 hours
  • Advanced
  • 50-300
What You'll Need
New Expansion Tank
Support Brackets
Tire Pressure Gauge
Teflon Tape
Bicycle Tire Pump
What You'll Need
New Expansion Tank
Support Brackets
Tire Pressure Gauge
Teflon Tape
Bicycle Tire Pump

Replacing your water heater expansion tank by yourself can save you a lot of money and time. With the right tools and this guide you will be able to replace the expansion tank on your water heater without calling a professional plumber. Just follow the steps below to safely replace your water heater expansion tank.

Step 1 - Identify Your Old Expansion Tank

The first step to replacing the water heater expansion tank is to locate it. The tank is usually located right next to your water heater and is connected to the water heater. Once identified, record the dimensions and connections to ensure when you purchase the new one it is going to fit and work properly. You can buy a new water heater expansion tank from the local hardware supply store or order online.

Step 2 - Turn Everything Off

flipping a circuit breaker in the panel box

Turn the water supply to the heater off by closing the shut off valve. The shut off valve may be near the heater or further up on the pipeline. If you don’t find it there, you can shut off the main water to the entire house.

Switch off the power supply to your water heater system by flipping the designated circuit breaker or turn off the main power to the house. Let the water heater cool down for some time. This could take an hour or so.

Step 3 - Drain the Water

Drain out the water from the water heater to reduce the water pressure. You can drain the water by opening the bleeder valve. Use the bucket to collect the water. Use caution since the water may be pressurized.

Step 4 - Disconnect the Expansion Tank

Disconnect the expansion tank carefully; watch out that the pipes and fittings are not damaged while removing the expansion tank.

Step 5 - Pressurize the Expansion Tank

With the water supply turned off make sure the pressure reading in the tank is “0”. Take a bicycle tire pump and attach it to the Schrader valve, you can find it at the bottom of the tank. Fill the tank with air to 12 psi or according to the amount indicated on the manufacturer’s instructions.

Step 6 - Check the Pressure

water pressure gauge

Check the pressure in the tank with a pressure gauge.

Step 7 - Teflon Tape

Get the Teflon tape and wind it around the ends of the connectors. Do not wrap the Teflon tape from the beginning of the connector, leave the first two or three threads bare or your tape will get into the system.

Step 8 - Install the New Tank

Install the new tank in the same position as the old one. Carefully connect the new tank to your heater system. Make sure the connectors are screwed on tight.

Step 9 - Check the System

You can now turn on the water supply. Check all the connectors to ensure there is no leakage.

Step 10 - Open a Faucet

Next, open a faucet and allow the water to run through the water heater system. Check once again if there is any leakage.

Step 11 - Switch on the Power Supply

Switch on the power supply for the water heater system and then turn on the water heater allowing it to heat up.

Step 12 - Hot Water

When the system has heated up, make one last check. Open the hot water faucet and check if the water flowing is hot.

How to Replace Your Water Heater Expansion Tank

Can I replace an expansion tank myself?

It is possible to replace an expansion tank as a DIY project, but it can be a rather difficult DIY. It is best if you already have experience with plumbing or if you have the task performed by a professional plumber.

You need to be able to accurately use and read a water pressure gauge, which requires some skill, and you need to install pipes and pipe fitting in a way that is both up to plumbing code and leak-proof. It will also be necessary to drain water and this can be a challenging DIY project physically.

For all these reasons, you may want to enlist the aid of a professional or another highly skilled DIYer who has experience with this type of project.

How do I know if my expansion tank is bad?

Expansion tanks make use of air that is already in the water heater system by design to keep water flowing through pipes. When the airflow is hindered, this can prevent hot water from flowing through the pipes.

What causes an expansion tank to lose pressure?

An air leak in the valve can cause an expansion tank to lose pressure. Without adequate pressure, too much water will enter the expansion tank.

What does it cost to replace an expansion tank on a water heater?

The price of a water heater expansion tank varies based on size and design but, on average, a standard tank will range from around $90 to $350 or more. The average cost is around $220.

Do I need to drain my water heater to install an expansion tank?

Whether you're adding a new expansion tank to an existing water heater or you are replacing a water expansion tank, you will need to drain your water heater. Various pipe connections have to be made and you don't want water to end up all over the floor, so drain the water heater before your work begins.