How to Flush a Tankless Water Heater At Home Step By Step

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Over time, your tankless water heater will build up a surface of calcium, and the filter will get blocked. Users should clean and plush properly a tankless water heater at least once a year to ensure longevity. This regular cleaning will improve the performance of your heater. While you are using it, make sure you clean the air filter and water bucket in the tankless water heater timely. How To Flush a Tankless Water Heater The following instructions will show you how to flush your tankless water heater thoroughly. These instructions will give you a general idea, and it is applicable to any heating component like this. You will need the followings to, How to Flush a Tankless Water Heater

  • Five-gallon bucket
  • Two stainless steel washing hoses
  • A submersible pump
  • Four gallons of white, food-grade vinegar

Disassembling the Tankless Water Heater and Draining:

First of all, you have to turn off the water pipe going into the tankless water heater and turn off the electricity. Now, you can open the service valve but be ready with your materials. Always keep in mind, power is not a thing to play. So safety first.

Now that your bucket is available for the water that will come out of the heater know that it will not squirt out, but it will instead be slow and drip down. If you think that it is too much to handle, then we are here to tell you that it is not.

However, we are sure that you do not want it on your garage floor. One of the things that you can do is, have the hoses ready they come along with the kit. You are supposed to place one end inside the bucket because whenever you unscrew the valve cap, you will be able to plug the hose into the opening.

Once you have done this, you will be able to redirect some of the water in the bucket.

Once you have cleaned the cold water side properly, you can move towards the hot waterside. The suggested temperature in the case of the water heater is 120 degrees Fahrenheit. You have to keep in mind that any carelessness can lead to burns, you have to protect yourself from burning. You might not have utilized the water for hot showers, and other purposes because when you are ready to clean it, the hot water might still be inside.

What you could do is that keep your hose and the bucket ready, as you did in case of the cold waterside. You are suggested to unscrew the hot water valve slowly until the water starts to drip out of it.

When you finally feel like the water is not hot or even if it’s warm, you can finish the unscrewing part, plug the hose and allow the water to drain in the bucket. Once you have completed the step of extraction of water, now the next step is to empty the bucket.

Injecting the Vinegar into the Tankless Water Heater:

Now comes the part where you fill the bucket with almost 4 gallons of food-grade, white vinegar. You can go to any good brand that you can find.

The next step is not a technical one; all you have to do is attach the hose that is going into the cold water, being careful about the fact that your connections are tight. You are not supposed to plug in the pump yet.

Now, you are recommended to place the pump inside the vinegar mixture right before plugging it into the wall. If there is no switch for switching on and off, then it will switch on as soon as you plug it in.

Now, it’s time to attach your hosses and submerge the pump in the mixture of vinegar.

You are ready to plug in the pump into the power. You should know that the vinegar will start to circulate in the cold water service valve. Which is blue, and will come out of the hot water service valve which is red then to the same bucket of vinegar.

You are recommended you leave it as it is for at least an hour to two hours. When the circulation of the vinegar is going on, meanwhile you can clean the filter. If you already do not know, then the screen of air intake is situated inside the tankless water heater.

You are not supposed to worry that it’s hard to get to it; all you have to do is remove the faceplate of the tankless water heater. When you unscrew it, the inner of the radiator will be exposed. Clean the filter as finely as you can and wipe it after rinsing the filter, re-install the filter after cleaning it.

Now you can put back the faceplate and let the water run through it for at least an hour.

Draining the Vinegar:

Now that the vinegar has run through the heater for more than an hour, the vinegar needs to be drained out.

Unplug the pump and let it drain in the bucket, not outside so that your grass or lawn is not damaged. Place the empty bucket under the heater and loosen the hose coming from the cold water side only and leave the hot water hose attached.

Descaling and Reassembling:

Now that the vinegar is out of the heater, you can open the levers coming from the cold water into the radiator and flow out of the hot water hose into the bucket. Once the hot water starts flowing out, close the cold water valve.

Now that the last traces of the vinegar has been cleaned out, it is time to reassemble the tankless water heater. Make sure that you tightly screw all the service caps. Now, you can turn on the cold water tap and let the water inside the tankless water heater. Turn on the electricity and your tankless water heater will work like new.


If you follow the given procedure, you can clean the Tankless Water Heater at home, and you do not have to pay loads of money to the plumbers.