Navien tankless water heater maintenance: Clean & Descale

Learn how to perform maintenance on Navien tankless water heater by cleaning and descaling the unit to improve the efficiency and for the long run.


This Ultimate maintenance guide will show you how to clean and descale your Navien tankless water heater. Suppose you had installed your water heater a year or two years ago and did not perform any maintenance on it. Now, it’s time for you to do it yourself. It’s simple and easy, and there’s nothing to be afraid of. We’ll guide you through the steps one by one.

In a tank-style water heater, minerals and sediments present in the water can rot and settle at the bottom of the tank, making it easy to flush and descale. However, a tankless water heater has a small heat exchanger, where the water goes through a heat plate which transfers heat into the water and comes out at the temperature you have set in the digital dial. This concentrated heat, with 240,000 BTUs, is five times stronger than a traditional tank-style water heater. It sounds like a tankless heater uses a lot of gas or electricity, but the good news is it only fires when you have a hot water faucet running in your house.

It is important to note that the concentrated heat exchanger needs to be flushed and cleaned at least every other year to keep the heater running like new. The heat exchanger can fail if not cleaned properly, which can lead to a short lifespan of the heater. If cleaned annually, there’s no reason why the heater can’t last for 30 to 50 years.

Tools required:

  • Phillips screwdriver
  • Channel lock Pliers
  • Pair of washing machine hoses
  • 3 Gallons of White vinegar
  • 1 Small Submersible pump between 1/4 to 1/6 HP.

You will need a Phillips screwdriver, a pair of channel lock pliers, and two clothes washer(washing machine) hoses. These can be easily obtained from amazon or any hardware shops. For flushing and descaling, you will need 3 gallons of white vinegar. After your first year, it is recommended to purchase a small sump pump which costs between $50-$60. It is important to ensure that the pump has a hose tap on the top to connect directly to one of the washing machine hoses. Make sure to choose a low-capacity pump like a 1/6 or 1/5th horsepower pump, so the vinegar can descale the heater slowly rather than pushing through too quickly and not effectively cleaning it.

The below table consists of components and tools used in maintainance process, we also included the best buy links.

1Descaling Flush Kit with pump
2Channel Lock Pliers
3Philips Screw Driver
4White Vinegar
5High Effective descaling solution
5Cleaning Brush
6Washing machine hoses 6Ft
7Navien Cold water inlet filter

How to Flush Navien tankless water heater

We are taking the example of Navien NPE-240A2 but generally all the other navien models are nearly same and you can follow the below tips to maintain them easily.

navien NPE-240A2 tankless water heater outer parts

Step1: Turn off the power supply

First, turn off the power at the power button on the heater dashboard and unplug the power cord from the power source. Then, turn off the gas supply to the unit if it is a gas tankless water heater. Remember that If the valve handle is running parallel to the pipe, it’s “open” or “on.” When it’s running perpendicular to the pipe, it’s “closed” or “off.”

When the valve handle is parallel to the pipe, the valve is in ON condition. If the valve handle is perpendicular to the pipe, it is in OFF condition.

turn off power supply and gas on navien tankless water heater

Step2: Remove the front panel

After completely removing the power supply, we must remove the front panel. It is attached with four screws, two screws on the top and two on the bottom. With the help of the Philips screwdriver, remove the screws and pull the front panel of the navien tankless water heater towards us carefully. All the internal parts and components are visible when the front panel is removed.

Step3: Clean the Air intake pipe filter

There are two pipes on the top of the heater, from which the left one is for air intake. A bird filter is located outside the pipe to prevent large creatures from entering the tankless water heater system. However, smaller insects, dirt, dust, and other debris may still enter, so a filter is in place to catch these particles. We will now proceed to clean it out.

how to remove air intake filter on navien tankless water heater

As you can see from the above image, there are two screws; remove the screws to get the air filter out. The air filter has a stainless steel mesh that blocks insects, debris, dirt, or small particles. So clean it with a brush or under tap water to remove the dust. You must clean the air intake filter every 3 to 4 months to avoid dust or insects blocking the air intake. If the air intake is improper, we get an “error code 110“.

After cleaning, place the filter as it is in the position and fix the screws, don’t tighten too hard. You can close the front panel now.

Step4: Close the water inlet and outlet valves

turn off inlet and outlet valves of navien water heater

Now close the cold and hot water intake valves to stop the water flowing through the system. The valves should be perpendicular to the pipe to do so.

Step5: Connect the washing machine hoses to service drain outlets.

Take out the drain cap and connect each clothes washer hose to the cold and hot water service drain outlets. You can just hand-tight them; there is no need to tighten them with a wrench.

Step6: Drain the water in the system completely

Now put both clothes washer hoses in the 5-gallon bucket and turn on or open both the service valves and the pressure release valve. As a result, water in the heater unit drains off completely. This water may be hot, so handle it carefully.

draining connection diagram of navien tankless water heater

Keeping the pressure release value open, open all the faucets connected to the hot water system to completely drain off the water, then close the pressure release valve.

Also read: Tankless Water Heater Expansion Tank: A Must-Read Guide Before You Buy

Step7: Clean the Trap

locating trap in the navien tankless heater

Between the cold water intake and hot water outlet, there is a trap, a cap-shaped plastic dust collector fitted with a pin. We will remove the pin from the trap and pull it down. Cleaning is necessary because much dirt and sediment accumulate in the trap, which we empty in a separate container and throw the dirty water away.

You will also notice that an O-ring comes out when the trap is removed. It is crucial to replace the O-ring in its proper place before putting the trap back in. We can clean the trap in a laundry tub and then reinsert it.

After cleaning the trap, we will place the O-ring over the trap seat and fit it onto the first ledge. We will then push it back into place. It should fit smoothly and seat flat against the housing. If it feels like it is turned in one direction or another, check to ensure the O-ring is not pinched.

Once it is in place, insert the locking pin back through the same two holes from which we took it out. And that’s all the trap has been cleaned.

Step8: Clean the Inlet water filter

locating inlet water filter in the navien tankless heater

Just before the cold water inlet connection, there is an Inlet water filter in black color and made of plastic. With the help of the channel lock, slightly loosen it and take it out with your hand. Look for dust or blockage, clean it, and put it back again. First, tighten it with your hand and then use a channel lock plier to tighten it like a 1/8th turn slightly. Don’t tighten it hard, as it is made of plastic it can break.

Step9: Flush the water heater to descale it

The final step is to flush and descale the heater. We will use a small sump pump and a clothes washer hose inlet. Place the pump inside a bucket, attach the cold side inlet to the top of it, and tighten it securely. Fill the bucket with two gallons of white vinegar.

flush navien tankless water heater with sump pump and vinegar

The sump pump, connected to the cold water inlet hose, will pump White vinegar through the hose into the cold water inlet of the water heater unit. The White Vinegar will flow through the heat exchanger and descales the mineral sediments. The vinegar, along with dirt and scales, leaves through the hot side and is diverted back into the bucket through the clothes washer outlet hose. Look at the vinegar coming out from the hose. The dirty vinegar represents more amount of mineral scales formed inside.

We will run this circulation of white vinegar through the system for approximately half an hour to 45 minutes to thoroughly descale the heater.

Step10: Clean the vinegar from the heater

purge vinegar from the tankless water heater

After flushing, we need to clean the vinegar from the heater. To do so, close the service drain on the cold side and then connect the clothes washer hose from the hot side to drainage and open the cold water intake valve. The Fresh cold water will purge the remaining vinegar out into the drainage. Run this for 1 or 2 minutes so the heater is cleaned with no vinegar.

Step11: Finishing and turning on the heater.

Turning on the navien tankless water heate after maintenance

Finally, turn off the service valves and remove the clothes washer hoses. Turn on both the cold water inlet and hot water outlet valves. Turn on the Gas Supply, plug the power cord into the power socket, and turn it ON. Next, turn on the heater by pressing the power button on the heater’s dashboard. Set the temperature to maximum and check the faucets for hot water.

With all this service maintenance on the navien tankless water heater is done and ready to use.

If you see no hot water coming through your navien tankless water heater, first try to reset the heater and then look for any error codes.

Related article: Tankless water heater leaking? find and stop the leak

If you have any questions or concerns, don’t hesitate to leave a comment below! Our team is here to assist you and provide all the information you need. Your feedback is important to us, so please feel free to share your thoughts and we’ll respond as soon as possible.

Joseph Miller

Joseph Miller is a highly experienced water heater repair expert with a passion for keeping homes warm and comfortable. With over 50 years of industry expertise, Joseph has developed a deep understanding of water heater systems and the intricacies of their repair and maintenance.

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  1. This step by step with pics is great! Thank you so much!

    At what step do we close the house faucets? We opened them to drain the system, but I’ve read this a few times and cannot find when to close all of them. Thank you in advance

  2. After flushing the system, we had an issue with flow from the faucets. We found that the aerator / screens in the sinks were filled with sediment. We discovered that the hot water outlet filter was full with sediment, and despite cleaning it daily, it still fills with sediment and some sediment still comes through the lines to the sinks. Inlet filter is always clear.

    Are we missing a step or process to bypass this filter when flushing since we have a recirculating pump?

  3. How do you deal with a heater that has a recirculation line incorporated into the mix? My heater has a recirculation line and I could not get the submersible pump to pump the vinegar through the heater. What am I doing wrong?

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