How to Clean Out a Water Heater Tank

August 24, 2020 |

Updated August 24, 2020

3 minute read

What is the procedure for cleaning out a tank with sediment?

Jerry L’Ecuyer & Frankie Alvarez

Dear Maintenance Men: My duplex has a 40- or 50-gallon water heater. What is the procedure for cleaning out the tank? I’m sure it has sediment, as our water is fairly hard. However, I don’t see a clean-out for the tank other than a drain valve.


Dear Frank: To get the most life out a residential water heater, a yearly tank draining and cleaning is recommended. Here is a quick run-through on how to clean the sediment out of a tank without a dedicated clean-out port.

1. Turn off the gas or electrical to the tank.

2. Allow the water in the tank to cool for at least two hours, or open a hot water valve, such as a bath valve, and let it run for about 10 minutes. If you are in a drought-prone area, just let the tank cool by itself.

3. Turn off the cold-water inlet valve for the tank and open a hot water sink faucet or bathtub valve to relieve water pressure in the tank.

4. Connect a hose to the bottom drain valve at the bottom of the tank.

5. Open the bottom drain valve to allow the draining of the tank. Be careful that the water is not scorching.

6. Once the water is all drained away, we suggest removing the drain valve at the bottom of the tank and inserting a cleaning brush to get rid of any debris still loose at the bottom of the tank. You might get a refrigerator coil cleaning brush, which is long and skinny and easy to insert through the drain opening at the bottom of the tank. (If the bottom drain valve is plastic, consider replacing it with a brass ball valve. This will ease future tank cleaning.)

7. Once all the water is drained out and before you remove the drain hose, it is sometimes recommended that you close all hot water faucets and repeatedly open and close the cold-water tank valve. Allow about a minute’s worth of water to escape under pressure to help clean out the last of any loose debris in the tank. Then re-close the cold-water inlet valve.

8. Remove the drain hose and close the drain valve.

9. Now you are ready to refill the hot water tank. Make sure the bottom drain valve is closed and a hot water faucet is open in the unit. (The open faucet will allow air to be purged from the water tank.)

10. Open the cold-water inlet valve leading to the water heater and allow the tank to fill. You will know it’s full when the hot water faucet in the unit stops sputtering air and only water is coming out of the faucet. It’s a good idea to open other hot water valves to help clear air from the lines as well.