How to flush a tankless water heater in 2022 – Complete Guide

The reason you are here is that you have got yourself a water heater problem and want to know “How to flush a tankless water heater in 2022.” Well, you are at the right place. We will make sure that you don’t have to keep searching anymore.

But before that, let us tell you what is likely to be the cause of it and how you can prevent it before it escalates into a bigger problem.

Why do we need to flush a tankless water heater?

Although the tankless water heater comes with the convenience of being cheaper and needing less space, it doesn’t mean that it does not require any maintenance. Because with time, your water heater will accumulate many scalps, which will make it harder for it to work correctly.

The scalp is a product of minerals (like calcium, magnesium, etc.) present in the water. It builds up when hard water (insufficient quality water) is heated up, which leads to the mineral being deposited on the heating element of the water heater. It makes it harder to heat the water quickly and also reduces the lifespan of your appliance. It can also clog the pipe from where the water will come out. So, it is recommended that you flush your water heater once a year or more, depending upon the water quality in your locality.

Precautions regarding flushing of water heater?

How to flush a tankless water heater doesn’t require any technical skills. So, house owners can also do it instead of hiring a professional. But caution is to be taken in doing so.

Make sure the water heater is power off before flushing. Check using a non-contact voltage tester. Sometimes, the heater is configured with more than one power source.

Instead of using heavy chemicals for flushing, use Virgin Food-Grade White Vinegar as it is recommended by most water heaters manufacturers.

Always refer to your owner manual for any specific instruction regarding the model before starting to do so.

What tools do you need?

Adjustable Wrench

Non-Contact Voltage Tester

Screw Driver

Virgin Food-Grade White Vinegar

A pair of 6-ft Washing Machine Hose

5 Gallon Bucket

Submersible Pump

Needle-nose plier


How to flush a Gas tankless water heater

Beware that the flushing method for gas or electricity-powered water heater differs from each other. Depending upon yours, read the respective one.

The whole procedure of flushing gas tankless water heater can be broken down into three phases:

Phase 1: Preparation 

First of all, shut down the power sources of the gas tankless water heater. To make sure it is powered off, use a non-contact voltage tester on wire inside the access panel as there could be more than one power source powering the heater. You can access it using a screwdriver.

Close the gas insulation valve. (insulation valves are present in most heaters. If yours don’t have one, contact your plumbing to install one as they are essential and convenient to use as they allow you to cut off water of gas without going through the lengthy manual procedure)

Close the cold and hot shut-off valves so that the freshwater does continue to replenish as you are cleaning the heater.

Carefully release the pressure relief valve. Be extremely careful as it contains hot water, mainly if the water heater was operating until a moment ago.

Locate the hot water and cold water service ports and connect the two hoses you purchased previously with them. one with each.

Now, connect the other end of the hose connected with the cold water services port to the submersible pump. Put the pump in the 5-gallon bucket.

As for the hose attached to the hot water service port, but it’s another end in the bucket.

Take the 4-gallon pure virgin food-grade white vinegar and fill the bucket with it.

You have completed all the preparation and are ready to start cleaning/flushing the gas water heater.

Phase 2: Flushing

Since everything is in place, open both the service ports of hot and cold water and start the pump.

Let the pump circulate the vinegar for a minimum of one hour. You may need to do it for longer if the pump is on the weaker side with a pumping speed of fewer than four gallons per minute.

The work of vinegar is done, and you can dump it. Remove the hose and the pump from the cold water service port and close it.

Release the cold water shut-off valve so that water can enter the unit and flush out the vinegar present in it into the bucket.

Once done, you can close the hot water service port and remove the second hose.

Flushing is complete.

Phase 3: Cleaning

Now that flushing is complete, you should take some time and clean the inlet filters present in the water heater before you start putting things back in their place.

Gently rinse the filter to remove any sediment or dirt stuck in the filter.

Put the clean filter back in.

Place the access panels cover back on and open the isolation valve.

Start the tankless water heater.


How to Flush a Electric tankless water heater

Flushing of an electric tankless water heater is much easier than the gas tankless water heater. But one thing should be known that checking the owner manual is extremely important as some models may have different instructions specific to that model. In which case, bashing through by the following instruction can damage the unit. Always consult the owner manual before following these steps.

Phase 1: Preparation 

Turn off the electrical power of the electric water heater.

Close the cold water shut-off valve so that the main water line becomes disconnected from the unit.

Use the faucets inside your house to drain the water in the unit.

Go ahead and close the hot water shut-off valve.

Take off the cover of the access panel. Check whether power is still being supplied to the unit or not using a non-contact voltage tester.

Once checked, remove the screws connecting the wire to the heating element of the unit.

Upon closer view, you can find a hexagonal brass top at the top of the heating element. Carefully remove the top. You can loosen and remove it by rotating it counterclockwise with the help of a wrench.

See whether there are any kinds of cracks or damages to the heating elements. If you see that they are damaged, then you need to replace them.

Place the heating element in the cooper chambers where they will be cleaned.

You have completed all the preparation and are ready to start cleaning/flushing the electric water heater.

Phase 2: Flushing

Submerge the heating elements in undiluted food-grade white vinegar inside cooper chambers.

Keep them submerged for around two hours. This will remove the scalp deposited on the heating element.

Drain out the vinegar and replace the heating element and hexagonal brass to their position.

Connect the wire with the heating element.

Open the cold water shut-off valve, which will make the water enter the unit and rinse it as well as the heating element.

Keep on letting the water flow so that it can be adequately rinsed and vinegar is washed.

During this, you can check for leaks or faults that may arise due to not fitting things back properly and correct them.

Flushing is complete.

Phase 3: Cleaning

Close the taps and the cold water shut-off valve.

Take a moment to clean the inlet filters of sediment and debris using cold water.

Replace the filters.

Replace the access panel.

You can now turn on the power of the unit.


Frequently Asked Questions

Do tankless water heaters need to be flushed?

Yes, most tankless water heater manufacturers recommend that one should flush their tankless water heater at least once a year to remove calcium and other mineral debris. At the same time, this frequency should be increased depending upon hard water. 

What happens if you don’t flush your tankless water heater?

The scalp is a product of minerals (like calcium, magnesium, etc.) present in the water. It builds up when hard water (insufficient quality water) is heated up, leading to the mineral being deposited on the heating element of the water heater. This makes it harder to heat the water quickly and also reduces the lifespan of your appliance. It can also clog the pipe from where the water will come out.

How much vinegar do you need to flush a tankless water heater?

For most tankless water heaters, 4-gallon undiluted virgin food-grade white vinegar is recommended. But it may change depending upon the model. So always consult your owner’s manual before deciding on what to use and how much to use.

Conclusion

Flushing/cleaning the tankless water heater is easy, and you don’t need to hire professionals to do it for you. By following the above steps, you can easily clean your tankless water heater and save your precious dollars. Similarly, the cost is incurred for the first time only, and for the following times, you only have to pay for the vinegar. Other supplies are reusable and, with proper care, can be used throughout the life span of a tankless water heater.

Hopefully, your issue is resolved. You can also see the FAQs above for additional answers related to how to flush a tankless water heater in 2022.


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Emma Johnson
By Emma Johnson

Hi, This is Emma. Author at “BestHeaterGuide.com”. I am a graduate of Mechanical Engineering. Currently researching on heating technology. However, I have learned many home heating techniques and still learning home heating technology. And I love to share my research and reviews.

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