How To Install Water Heater Expansion Tank | 10 Easy Steps of Installation

how to install hot water heater expansion tank

Have you ever wondered why most homes install water tanks for water heaters? well, the water heats up when it swells. If your tank has the capacity to hold 50 gallons of water, it can be expanded to 52 gallons or more of water when the water is heated?

So where’s the excess water? Your guess is as good as mine, your expansion tank.

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In the past, excess water returned to the city to supply water. However, there is a possibility that water in your home can contaminate the public water supply. As a result, plumbing standards have been changed and families should avoid reflux.

Without inflated water tanks, the water will have nowhere to go. This condition significantly increases the pressure of water pipes and can lead to damage to pipes, household appliances and water heaters.

Handling of the damaged plumbing system will be very stressful, so installing the expansion tank will be a good way to avoid unnecessary pressure.

Now, the question is how to install an expansion tank on a gas water heater.

well, that’s the purpose of this article. Let’s run step-by-step instructions on how to install an expansion tank on your gas water heater. Installing the expansion tank can be a job done yourself – as long as you have the right tools and the right guide, you will be able to install your expansion tank in no time.

So, first thing. What do you need for installation? The good news is that you don’t need a lot of tools to install. You just need to prepare these materials:

  • Tubular wrench
  • Water heater expansion tank
  • Polytetrafluoroethylene tape
  • Drilling equipment
  • Screws
  • T-shirt accessories or saddle valves

Now, we will guide you through the step-by-step installation guide:

Step 1: Determine the water pressure

Before starting installation, it is essential to determine the water pressure at home. You must check and record the water pressure using the pressure gauge within 24 hours.

The recommended water pressure is 50 to 60 per square inch (psi). If your water pressure is greater than 80 psi, then you need to install a pressure relief valve.

Step 2: Determine the size of your thermal expansion tank

For housing, an expansion tank of 2 to 5 gallons is usually used. If you are not sure, it is better to install larger sizes. The pressure relief valve is discharged because the pressure is too high.

Step 3: Turn off the water supply

To ensure the safety of its installation, be sure to turn off the water supply. Close the water from the main water supply line.

Step 4: Turn off the gas

If you are using a gas water heater, turn off the gas supply of the heater. If you do not know how to turn off the gas supply, contact your gas company and let them do the job.
This is very important, because if this is not done correctly, dangerous gases can accumulate in your house, a small spark can ignite them, which leads to a more serious danger. This harmful smoke can also bring illness and death to your family, if you enter your home.

Step 5: Find the cold water supply

The expansion tank is usually connected to the cold water supply, so you need to determine which pipes are cold water supply.

Step 6: Install your expansion tank

Hang the expansion tank above the cold water supply. Make sure that it can enter through the horizontal part and the water heater.

If you are using a saddle valve, you just need to screw it correctly and no welding is required.
Once the water swells, it will carry an extra weight, so you should be able to hold the extra water it will carry. If the expansion of the tank will fall, you can damage your water heater and the surrounding area.

Step 7: Connect the tank

After that, use your polyfluoroethylene tape at the end of the connector and tighten the connection with a wrench. Be sure not to tighten the connection too much so that it does not break.

Step 8: Check the pressure of the expansion tank

Then adjust the air pressure. It should be the same as the maximum water pressure at home. Use a manual pump to regulate the pressure, because if you use an air compressor, you can break the air bag.

Each expansion tank has an air bag, which is pressurized with air. It swells and shrinks absorbs the expanded water from the water heater.

Step 9: Clean the trapped air

Turn on the gas heater and water supply. Then open the hot water tap until the flow stabilizes, removing trapped air from the other side of the bladder.

Step 10: Check if it works correctly

Assuming that the expansion box works well, its diaphragm will separate water and air. Air should be at the top, while water should reside at the bottom.

First, you can click on the top and bottom parts of the tank. If you click on the top, it gives a hollow sound, then your expansion box works fine.

Another way is to check the temperature of your tank. The upper area should be cold, because this is the location of the air. The bottom should be warm, because this is the place where heated water is stored.

Finally, you can check the pressure inside the expansion tank with a manometer. The result should be the same as the manufacturer’s specifications. If the pressure inside the water heater is high, the expansion tank does not work properly, which can cause dripping.


There you go! You can do it yourself, or you can seek help from the pipe. Either way, it is important to install the expansion tank on your water heater to avoid any damage to the pipes.

If you decide to do it yourself, be sure to follow the step-by-step guide provided above. You should also pay attention to the above-mentioned precautions in the event of an accident and allow you to successfully install your water heater expansion tank.

In some places it is necessary to install expansion cans, because regulations require them to do so. Review the regulations in your area to make sure you meet the requirements.
Think of the expansion tank as the prevention of a major problem – a pipeline disaster. With an expansion tank, the pressure will be regulated and excess water can be stored.

We hope to be able to provide you with a complete guide on how to install an expansion tank on a gas water heater. If you can successfully install the expansion tank, let us know in the comments section.

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