How to Fix a Leaking Expansion Tank for a Water Heater

Preparation

Step 1

Turn the valve on your water heater’s water-supply line clockwise to shut the water supply off to the tank.

Step 2

Turn off the breaker in the main panel to shut down an electric water heater.

Step 3

Turn off the gas to a gas water heater by turning the gas control valve to the off position on the water heater.

Replace Thread Seal Tape

Step 1

Remove the existing expansion tank using an adjustable pipe wrench and turning the tank counterclockwise at the top where it attaches to the pipe fitting. Have a partner support the tank to keep it from falling to the floor.

Step 2

Clean the threads on the expansion tank. Remove any dirt, grim or old thread seal tape from the threads with an old cloth.

Step 3

Wrap the threads in two or three layers of new thread seal tape. Reattach the tank to the fitting and tighten it with the pipe wrench

Step 4

Turn the water supply back on to the water heater. Turn on the water or gas, and light the pilot on the gas water heater.

Step 5

Watch for additional leaks from the tank. If your expansion tank continues to leak, you must replace the tank.

Replace the Expansion Tank

Step 1

Turn off all the water faucets inside your residence. Attach a water-pressure test gauge to an outside faucet. Turn on the outside faucet to get the pressure reading. Note the pressure reading on the gauge.

Step 2

Attach a bicycle pump or air compressor to the changing valve at the bottom of a replacement expansion tank if you need to increase the pressure in the tank above 40 pounds-per-square-inch.

Step 3

Check the pressure in the tank with a with a tire-pressure gauge. Add or release air from the expansion tank until the pressure in the tank equals the water pressure in your home.

Step 4

Turn off the water supply to the water heater. Turn off the water gas or electric water heater. Remove the current expansion tank with the adjustable pipe wrench.

Step 5

Wrap the threads of the replacement tank with about three layers of thread seal tape. Screw the tank into the fitting and tighten it with the wrench.

Step 6

Turn on the water supply and the gas or electricity to the water heater.