Everything You Need to Know About How to Service Tankless Water Heaters

Being without hot water is a pain – no one likes taking a cold shower! Although it is something that many of us take for granted, our water heaters seem to fail at the worst times. Preventative maintenance can really help with future problems.

What Are Tankless Water Heaters?

how to service tankless water heater

When it comes to water heaters, tankless water heaters have increasingly gained popularity due to their continuous supply of hot water for the entire household. 

These high-tech units provide a smart, energy-efficient solution to your hot water woes; however, they require occasional periods of service and maintenance. To do so, you don’t always have to call in a professional; you can easily learn how to service tankless water heater and do it yourself at home.

The following guide will help you understand why tankless water heaters are the water heaters of the future and help you learn how to service tankless water heaters at home.

Servicing the Tankless Water Heater: Learning the Ropes

Flushing Out the Debris and Sediment Deposits

When it comes to proper service and maintenance of your tankless water heater, flushing it at least once every two years is a must. Tankless water heaters are susceptible to build up of minerals and sediments that can accumulate over time. 

This affects their efficiency and life expectancy while damaging the heat exchanger in your unit simultaneously. This is something you want to avoid at just about all costs. Not only this, but if left ignored, it could leave you with an expensive energy bill at the end of the month, causing damages that are not covered under warranty in the process. 

As a result, learning how to service tankless water heaters or calling in professionals to do the job has become extremely important. If you plan to service the heater yourself, the process is fairly simple.

  1. Start by turning off the power source for the tankless water heater, which is usually the main gas line or the circuit breaker for electrical devices.
  2. Now turn off the three water valves attached to the tankless water heater. These valves are usually colored red and blue, along with a third main valve. Doing so prevents cold water from flowing into the heater and hot water from coming out. This makes the cleaning process much easier and more manageable. 
  3. Next, identify the purge valves on the water heater (these are usually designed in the shape of the letter T). Simply remove the purge port caps from the hot and cold valves. This is done to relieve any buildup pressure inside the valves so the water doesn’t come gushing out on you upon contact. While doing so, be careful not to damage the rubber washer sealing discs since these are essential for the proper functioning of the valves.
  4. Once you are done with the purge valves, try attaching the hosing lines to all three valves. Your hosting lines should be long enough to cover the distance between the tankless water heater and the bucket. In case your heater did not come with a hosing line, you can easily purchase one from a home repair or a hardware store. They are relatively inexpensive to purchase and install on your own.
  5. If you are a novice and still learning how to service a tankless water heater, try referring to the instructions in the manual. Given that the process is pretty straightforward, the manual should give you all the information and answers you need.
  6. After connecting the hosing line securely, open the purge port valves. This can easily be done by gently twisting the valves perpendicularly in the position of the hot and cold valves.
  7. Once your water heater is set up for servicing, pour about 2½ to 3 gallons of undiluted white vinegar into a separate bucket to clean the heater. There are chemical cleaning solutions available on the market as well, but white vinegar is a budget friendly option. Plus, since your tankless water heater is most likely the source of your drinking water, it’s better to steer clear of the chemicals and stick to the good old-fashioned white vinegar.
  8. Flush and drain the heater using the white vinegar mentioned above. This can take anywhere between 45 minutes to an hour. You may refer to the instruction manual to understand the procedure better.
  9. Once you are done with the flushing, twist the T-shaped handles and close the purge port valves.
  10. Gently disconnect and remove the line housing from the valves, followed by replacing the purge port valve caps on the purge valves the same way you removed them. Remember to close the caps firmly while keeping an eye out for the rubber sealing discs in the caps at the same time.
  11. Now safely restart the tankless water heater by opening the hot and cold valves, and then open the main valve. In case you are unsure or in doubt about which valve is which, look back into the manual for the exact instructions.
  12. Finally, open the hot water tap slowly into the sink for 2 to 3 minutes so that all the air can pass through the pipe and the water can start running steadily.

While flushing is undoubtedly the most important aspect of learning how to service a tankless water heater, flushing alone isn’t enough to promise the heater’s longevity. 

There are other aspects to cleaning, servicing, and maintenance that you must pay attention to as well to ensure that your tankless water heater lasts you a long time. Keep reading to learn how to individually service tankless water heater parts below. 

Servicing the Air Filters

Regular service and cleaning of air filters are just as important as flushing the heaters. To service the air filter:

  • Start by removing them from the water heater.
  • Take a soft brush and clean the filters using a soap and water solution.
  • Clean the filter gently but thoroughly to ensure proper airflow.

Once cleaned, rinse the air filters with cold water and allow them to dry completely before placing them back in their place. If you are unsure how to remove the air filter, refer to the manufacturer’s instructions.

Periodic Pipe Maintenance

Tankless water heater pipes are yet another key critical component when it comes to servicing and maintenance. This is especially important if you live in areas with a colder climate. The water heater pipes must be inspected at regular intervals for any cracks or damages to help protect your heaters from any possible hazard or even flooding of homes due to a pipe burst.

Water Heater Exterior Maintenance

While learning how to service tankless water heater’s interior is crucial for ensuring that you get a steady supply of clean water, you must also pay attention to keeping the exterior clean as well. To do so, simply cut off the heater from the power and water supply. Now take a clean damp cloth and wipe down the tank’s exterior

This will aid in getting rid of any dust, germs or debris that may have accumulated on it over time. This is important because these types of seemingly harmless debris can prove to be quite hazardous to health if they creep into the heater.

Inspecting the Pressure Relief Valves

Another crucial inspection involved in learning how to service tankless water heaters is the periodic maintenance and examining the pressure relief valves. These valves are usually located at the top of the heaters and are responsible for lowering the internal tank pressure when it gets too high by releasing some of the water. 

By ensuring that the pressure relief valves are working fine, one can save themselves from worrying about fluctuations in pressure to avoid any potential water heater catastrophes.

Top Reviewed Tankless Water Heaters of 2022

In case you are still trying to decide which tankless water heater to buy, then below is a comprehensive list of some of the top reviewed tankless water heaters of 2023.

  • EcoSmart ECO 27
  • Rheem 18kw Tankless Electric Water Heater
  • Stiebel Eltron DHC Trend Point-of-Use Electric Tankless Water Heaters
  • Rheem 13kw Tankless Electric Water Heater RTEX-13
  • Eemax 27kW Electric Tankless


Tankless water heaters offer a smart, cost-effective, and energy-efficient solution to your water heating woes. So now that you are well aware of the top tankless water heaters and why they need periodic servicing and maintenance, you must learn how to service tankless water heaters at home. 

From taking care of simple tasks like wiping clean the exterior to flushing out unwanted deposits – all can be done at home. All you need is a bit of practice, a little while to get yourself oriented, and a thorough reading of the instruction manual. Good luck! 

With years of experience under his belt, Adam decided to put his water heater knowledge to work. By providing high-quality content and expert guides, Adam hopes to help anyone looking for expert water heater advice.