Navien Tankless Water Heater Maintenance

Navien Tankless Water Heater Maintenance [Complete Guide]

This is a complete guide on Navien Tankless Water Heater Maintenance. From this guide, you will learn: 

  • The schedule of Navien tankless water heater maintenance or when you should clean the unit
  • The step-by-step maintaining procedure 
  • How to protect the water heater from freezing

In short, you can learn everything you need to know about tankless water heater maintenance, which will help prolong the water heater life. 

So, stay in tune with this guide till the end. 

Table of Contents

Navien Tankless Water Heater requires both periodic and annual inspection. In short, you should inspect some parts of the unit periodically. And other parts of the water heater needed to be maintained annually. 

The parts that need periodic inspection and service are: 

  • The exterior of the unit or the outside body
  • Cold water inlet filter
  • Recirculation inlet filter

You should also drain the unit every six month to remove sediment build ups from the unit.

On the other hand, the air intake filter of your Navien tankless water heater should be inspected and serviced every 3-4 months. 

Lastly, you must flush the heat exchanger every year. However, don’t hesitate to flush the heat exchanger every six month if you live in a hard water area or you operate the unit at a higher temperature setting. 

Maintaining a tankless water heater seems like a pain in the butt. But this short-term pain will give you ultimate comfort for the next 15-20 years by delivering hot water everyday. 

This chapter will make the water heater maintenance workflow easy by letting you know how to service your Navien Water Heater efficiently. Without a second delay, let’s get started. 

Cleaning The Exterior Of The Unit:

Let’s start from the basic cleaning workflow. First off, clean the exterior of your tankless water heater. 

Take a damp cloth and wipe the outside of the unit to clean the water heater. Ensure you wipe every section, the front panel, and bottom ports of the unit evenly. 

To remove any surface stains, use a non-acidic and non-abrasive cleaner. Try to keep the front panel dry as possible as you can because it’s not waterproof. 

Cautions: Before wiping the water heater, you must turn the unit off and disconnect it from the electric power supply. The water heater will remain hot for a couple of minutes after turning it off. So, wait until the unit cools down completely to avoid possible burning accidents. 

Draining Navien Tankless Water Heater:

Before performing maintenance tasks like cleaning the inlet water filter, draining your tankless unit is a prerequisite. Therefore, it will protect your water heater against freezing when you will not use the device for an extended period. 

Follow the step-by-step draining procedure below to drain the water heater like a charm: 

  1. Turn off your water heater by pressing the Power button on the front panel.
  2. Place a plastic bucket under the unit to catch residual water coming out of the unit. 
  3. Shut the gas supply off to the unit by turning the gas valve clockwise. 
  4. Shut off the water supply to your water heater by closing the water supply valve on the inlet. 
  5. Open every hot water faucet everywhere in your house to quicken the draining process. 
  6. Pull out the recirculation inlet filter, which you can find at the bottom of the water heater. 
  7. Open the pump drain plug if it’s an A2 model. 
  8. Remove the cold water inlet filter and let the water drain out of your water heater. 
  9. Once you drain out the water completely, reinsert both the recirculation inlet filter and the cold water inlet filter. 
  10. Now, refill your water heater by following the steps above in reverse. 

Flushing the Heat Exchanger

To maintain proper water heater operation, you should flush the heat exchanger annually. In short, every water heater manufacturer recommends you to flush the unit once a year. 

However, if the water you get is excessively hard, you should flush the heater every six months. 

You will not get enough hot water if the heat exchanger gets clogged by scale buildups. To avoid such incidents, flushing the water heater is a must. 

Ensure you have the following pieces of maintenance kit before flushing the Navien Tankless Water Heater: 

  • A 5-gallon capacity plastic bucket
  • Cleaning solution like diluted white vinegar 
  • Two garden hoses
  • A water circulation pump 

Once you have these kits at your fingertips, go along with the following steps to flush the water heater: 

Flushing Navien Heat Exchanger
  • Shut off the unit by pressing the Power button on the front panel.
  • Detach your water heater from the power supply. 
  • Close both the C and D valves on the hot and cold water lines.
  • Attach one hose to the A valve and leave the other end of the hose in the plastic bucket. 
  • Connect another hose to the circulation pump outlet and the cold water line at the B valve. 
  • Attach the 3rd hose to the circulation pump inlet and place the other end of the hose into the bucket. 
  • Pour the diluted white vinegar into the plastic bucket. 
  • Open both A and B valves. 
  • Turn on your circulation pump to let it circulate the cleaning solution through the water heater. You should run the pump for at least 45 minutes. 
  • Now, it’s time to rinse the cleaning residue from the unit. So, remove the free end of a hose from the bucket and leave it in the condensate drain or laundry tub. Close the B valve and open the D valve. Next, allow the water to flow through the unit for 5 minutes. Lastly, close the A valve and open the C valve.
  • Detach every hose from the water heater. 
  • Remove the cold water inlet filter and rinse it to clean any residue.
  • Reinsert the filter and ensure you tighten up its cap. 
  • Finally, press the Power button to turn the unit on.

Washing the Cold Water Inlet Filter and the Recirculation Inlet Filter

Cleaning the cold water inlet filter and recirculation inlet filter

Cold water inlet filter and recirculation inlet filter on your Navien Tankless Water require periodic inspection. If these two inlet filters get restricted by dirt, debris, and lint, it will disrupt the normal water heater operation.  

I recommend you follow the steps described below to clean these two inlet filters: 

  • Drain your water heater. 
  • Remove the recirculation inlet filter and the cold water inlet filter from the water heater. 
  • Rinse these two filters with clean cold water. If needed, scrub those filters with a soft brush and wash them with water. 
  • Reinsert those two filters into their places and tighten them up. 
  • Finally, refill your water heater. 

Cleaning the Air Intake Filter

Navien Air Intake Filter Cleaning

Like the cold water inlet filter, you should also inspect the air intake filter periodically. Specifically, I recommend you check this filter every 3-4 months. 

If the air intake filter gets clogged by lint or debris, your Navien tankless water heater won’t work and shows the error code E110. 

You must release the blockage from the filter to bring the water heater back to its operating condition. Check out the following steps to clean the air intake filter: 

  • Shut down the unit by pressing the Power button.
  • Unplug your water heater from the electric power supply. 
  • Remove the front cover from the unit. 
  • Unscrew the nut that secures the air intake filter in its place. You can find the filter at the top left of the water heater. 
  • Remove the filter assembly. 
  • Pull out the filter from the plastic assembly and clean it by scrubbing a toothbrush and rinsing with cold water.
  • Air dry the filter. You can also use a dry towel to dry the air intake filter. 
  • Reinsert the filter into the plastic assembly.
  • Replace the air filter assembly back into the unit and secure it by tightening up the nut. 
  • Put the front cover back into its place.
  • Plug the water heater into an electric outlet. 
  • Turn on the water heater by pressing the Power button. 

Protecting The Unit From Freezing

The Navien limited warranty doesn’t cover the damage from freezing. Generally, freezing damage occurs because of back drafting caused by negative pressure in the building. 

It’s not a manufacturer defect. So, you will get no warranty benefits if the damage comes from freezing. 

I highly recommend the use of direct exhaust vent and intake system to avoid the freezing damage. You should also maintain the following guidelines to avoid freezing issues:

  • Never disconnect the unit from the electric power supply except for routine maintenance. The Navien tankless water heater comes with a freezing protection feature. The freeze protection system requires electricity to function properly. 
  • If you own the A2 mode, never close the gas valve except for routine maintenance. 
  • Drain the water heater if you are not going to use the unit for an extended period. 

However, if you suspect the tankless water heater gets frozen and no hot water is flowing, follow the steps described below: 

  • Turn off your water heater.
  • Close the gas valve.
  • Open the hot water faucet that is near the water heater.
  • Heat up both the primary and the secondary heat exchangers by using a hair dryer or a portable electric heater. 
  • Check every minute to see if water is running at the open faucet. 
  • Inspect the water heater and piping for leaks when the water starts flowing again. If you find any leaks or the unit is not functioning properly, call a licensed plumber for help. 


How much does it cost to maintain a tankless water heater?

You should spend around $200 to $600 to maintain and service your electric tankless water heaters. 

How often should you flush a Navien tankless water heater?

You should flush your Navien Tankless Water Heater every year. However, it’s recommended to flush the unit every six months if the water you get is excessively hard. 

Do tankless water heaters require annual maintenance?

Yes, tankless water heaters require annual maintenance to maximize the overall performance, heating efficiency, and durability. 

How long does a Navien last?

You can expect your Navien Tankless Water to last up to 15-20 years if you maintain it routinely. 


Servicing your Navien Tankless Water Heater routinely will prolong the overall durability of the unit. It will also keep the unit functional for years to come. So, you must maintain your water heater periodically and annually. 

And on the guide, I broke down everything about water heater maintenance. Just follow the direction I mentioned and service the unit like a pro to maximize its performance and overall life expectancy. 

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