How to Clean a Tankless Water Heater?

A tankless water heater is a very reliable heating system that is a must need for every homeowner. It is energy efficient and not only that; you will be able to use it for more than two decades if you can do the maintenance

During the time a customer goes to the shop to buy a heater, the manufacturer always tells them to clean it once every year. This process will prevent materials like calcium or other things to form in the heater with time. Even hard water imposes a negative impact on this heating system.

So, from the following article, you will get the proper ways to clean a tankless water heater in a very easy way. Read in to find out more.

Equipment Which Is Necessary

  • Tester (electrical)
  • Screwdriver
  • Wrench
  • Sump pump (small size)
  • Bucket (4-5 gallon)
  • 2 Garden hose with connectors (6 foot)
  • White vinegar (4-5 gallon)



Below, you will find out the step by step guideline that you can follow in order to clean the tankless water heater.

  • Step 1

Turn off the tankless heater before you start the cleaning process. If you are using the electric one, make sure the electrical circuits are all shut down completely. For the gas unit, you can simply turn off the gas supply line by rotating the valve in an anti-clockwise direction.

  • Step 2

Now, you have to remove the cover of the heater carefully. Use the screwdriver to help you with this task. Go to the wiring unit, but don’t touch it as it is very dangerous for you. Take the electrical tester and put it in the wiring area.

If you see that the light from the tester just turned on, it means that there is still some electricity running. Re-check all the connections, including the circuit breakers, and keep using the tester until the lights are not showing up from it.

  • Step 3

There is a supply valve that creates a pathway for the cold water to move towards the heater. You must turn it off and do the same thing for the hot water valve. This valve plays the role of distributing hot water to your appliances.

  • Step 4

Connect the hose with the sump pump. Use the other end to connect it with the cold water isolation valve. Then, pick another hose and connect it with the hot water isolation valve. Check whether the couplers are properly getting tight or not. You can do this with the help of the wrench.

  • Step 5

How to Clean A Tankless Water Heater

Put the pump and the second hose (open end) into the bucket. Gently fill the bucket with the white vinegar. Don’t be in a hurry, take some time and patience.

  • Step 6

Go to the hot and cold isolation valve on the water and open both of them. When everything is set, turn on the pump that is placed in the bucket. This process will help the vinegar to circulate throughout the heater.

  • Step 7

Do it for around 45 minutes and then turn it off. Give some time to let all the vinegar to flush from the heater straight to the bucket. After it is done, close the isolation valve of the cold water.

  • Step 8

Remove all of the vinegar from the bucket and place the hose (open end) again inside the bucket. Open the cold water supply valve and give around 4-5 minutes to let the water run into the bucket. Then turn it off and remove the hose from the inlet valves.

  • Step 9

Turn off the isolation valve of the hot water. You will find an inlet filter screen in the heater. For further clarification, you can go through the instruction manual. Clean the screen to remove any kind of residue sand, and when it is done, put it back onto its original position.

  • Step 10

First turn on the hot water supply valve then, do it for the cold water one. For safety purposes, open some of the faucets inside your home to release any kind of hot air that could remain stuck.

Check it constantly, and when you are feeling no hot air getting released from the faucet, turn it off.

  • Step 11

Go through all of the connections to detect any kind of flaws like leaks, loose connections, etc. Turn on the gas supply valve along with the circuit breaker and enjoy the fresh hot water. Congrats! You are finished with the cleaning work.


Getting the right tankless water heater is a very important step for every homeowner. After all, you will always prefer your investment to be beneficial for you.

Go through the steps a couple of times so that you can remember it when you are in need of it.

Best of luck with the cleaning!