Navien Tankless Water Heater Error Code E110 [Fixed A-Z]

If you look up the Navien tankless water heater error code E110 in your owner’s manual, you’ll find that it refers to abnormal air pressure. There are many potential causes behind this issue. But from my own experience, I can tell you that the most common one is obstructions in the exhaust pipe.

Besides that, issues like a clogged air intake filter and a dirty air intake can also cause this error code. On top of that, condensation inside the unit can also lead to the error code E110.

There are a lot of possible reasons that could make this error code come up in your water heater. So, let’s dive right in!

navien tankless water heater error code e110

In this section, I’ll talk about the main reasons why the Navien E110 code is displayed in your heater along with their solutions.

01. Blocked Exhaust Pipe

The number one reason behind getting the E110 error code is a clogged exhaust pipe. If anything is blocking it, the exhaust gases won’t be able to go out easily. So, that would create an abnormal air pressure issue. More often than not, it will be dirt that blocks the exhaust.

exhaust pipe of navien tankless water heater

However, it doesn’t have to necessarily be dirt or dust that’s blocking up your exhaust. It could be all sorts of things like a dead animal too. If you live in a cold area where the temperature gets low, there could be ice blockage piled up on your exhaust. Any of these blockages can lead to this error code.

Inspecting the exhaust pipe is easy enough. You just have to go to where it leads and check it physically. If anything is blocking the exhaust pipe, you should be able to easily spot it. If you don’t see anything on your exhaust, then this is not the issue that’s causing the E110 code.

How To Fix:

If you see any blockage on the exhaust pipe, then it’s your job to remove it. Hopefully, the abnormal air pressure issue will be fixed when you do that and the error code will go away.

How To Remove Navien Tankless Water Heater Exhaust Blockage?

In all honestly, the work that it takes to remove the blockage depends on what you’re dealing with. If it’s simply a dead animal, you can just pick it up and put it in the trash can.

If it’s a blob of dirt, you have to do a bit of cleaning there as well to make sure any residue doesn’t go into the exhaust. When dealing with ice blockage, you may have to remove it by beating it with a shovel or an axe.

You can also use a vacuum cleaner to clean the exhaust pipe if you need it. Just place it at the end of the exhaust pipe and let the cleaner work its magic. No matter what the obstruction is, the task at hand is to remove it so that the error code can go away.

If the error code doesn’t disappear after removing the debris, you should reset the water heater. If the issue remains, then you need to do a better job cleaning it and then, reset the water heater again.

02. Clogged Air Intake Filter

It’s extremely annoying when you’re in the middle of taking a shower and the hot water flow suddenly gets replaced with cold water. To make matters worse, you see the error code E110 pop up. If the exhaust wasn’t obstructed or cleaning it didn’t work, the next most likely culprit is a dirty air intake filter.

The job of the air intake filter is really important. It makes sure that clean air goes into the water heater when required for combustion. Due to that, the dirt piles up on the air intake filter itself.

You can easily inspect if this is the issue that’s causing all the ruckus with the error code. You can follow these simple steps to inspect the air intake filter in your Navien tankless water heater:

Step 01 – Remove The Front Panel

Turn off the power to the unit by pressing the power button and you can also unplug it from the power outlet for additional safety. Remove the screws that hold the front cover in place as you’ll have to remove them to access the air intake filter.

Based on the model you’re using, you may have to unlock some tabs at the top and bottom of the water heater. So, the process can be different depending on your heater but the key step here is to remove the front panel of your water heater.

It should be an easy job to do. However, if you’re facing any issues, you can check your owner’s manual for detailed instructions on how you can remove the front panel of your water heater.

Step 02 – Locate & Remove The Air Intake Filter

Once you take off the front cover, you’ll see the air filter at the top of the heater. It’s located in the upper left-hand cover of your heater and right under the point where the air intake connects with the water heater. If you’re having any difficulty locating it, here’s a picture to help you out:

air intake filter of navien tankless water heater

The next step is to remove the air filter from the heater so that you can inspect it.  In order to do that, remove the screw that holds the air intake filter in place. Be careful not to drop the screw inside the water heater once you remove it.

Place a hand under the screw as you remove it so that you can easily catch it when it comes off. Once you remove the screw, you should be able to easily pull out the air intake filter.

Step 03 – Inspect The Air Intake Filter

At this stage, you can take a good look at the condition of the air intake filter. If it’s dirty, you may have found your culprit. If you haven’t done any maintenance jobs on your water heater before, you may be surprised at how dirty it can get. Here’s an example of how dirty an air intake filter can get:

clogged air intake filter of navien tankless water heater

In this case, it was grass that clogged up the air intake filter and messed up the airflow. But it could be a lot of other types of dirt as well. However, there’s also the chance that the air intake filter is clean. If that’s the case, then another issue is the main culprit behind the E110 error code.

How To Fix:

If the air intake filter is dirty, you’ll have to clean it. The good news is that it’s super easy to clean it. You can easily do it on your own. Just remove the dust or objects that have piled up on the filter and throw them in the bin.

Once you do that, you can rinse the filter in running water until it’s clean. If the filter is too dirty, you can also clean it with soap and water. Here’s an example of what a clean air intake filter looks like:

clean air intake filter of navien tankless water heater

Keep in mind that you shouldn’t place the air intake filter back in immediately after cleaning it. Use a towel and give it some time to dry properly. Only then, you can place the filter back in.

Once you do that, attach the screw and tighten it to secure the filter in its place. Then, you can secure the front cover in its place and restore the power supply to the water heater.

Hopefully, the error code will go away and your heater will work fine after you do that. Sometimes, the error code won’t go away on its own. In that case, you’ll have to reset the water heater. Stick around to find out how you can do that as I’ll also talk about that in this guide.

03. Obstructed Air Intake

Now, it really shouldn’t come as a surprise that a dirty air intake is on the list. As it’s a matter of an issue related to abnormal air pressure, it’s understandable that the issue is to occur somewhere in the airflow. If it’s not the exhaust, there’s a good chance it could be the intake.

air intake of navien tankless water heater

Just like the exhaust, similar issues can clog up the air intake. If there are any issues with the Navien tankless water heater venting, that can bring up the E110 error code. It could be dirt, dust, debris, dead animals, insects, or ice blockage that causes this problem.

How To Fix:

You have to remove the dirt from the air intake. The process of doing it would be similar to what you did to the exhaust pipe. When you’re cleaning the exhaust, it’s a good idea to clean the air intake as well.

In most cases, they would be located in close proximity and you should be able to clean one after the other right away. Hopefully, cleaning the air intake pipe will get rid of the error code in your water heater.

04. Build-up Of Condensate

You already know about the three major reasons behind the E110 error code and their fixes in this guide. In all honesty, the error code should go away if you’ve tried all of them and reset the water heater.

But there are some rare cases when the error code can come up due to other issues. Yes, I am talking about the build-up of condensate in the water heater and you’ll find it in the condensate drain.

Even in a Navien NPE-240A, the error code E110 can come up due to this issue. You need to inspect the condensate drain that’s located at the bottom of your water heater to see if it’s the culprit.

condensate drain of navien tankless water heater

It’s a bit unclear why this happens as condensate shouldn’t have any effect on the airflow. But I can tell you from personal experience after working on many heaters that it does happen sometimes.

How To Fix:

You’ll be happy to know that fixing this issue doesn’t take much work at all. You just need to pull out the condensate drain after pulling the tab and get rid of the condensate inside it. Then, put it back in its place and secure it. Reset your water heater after doing it and the error code should go away.

How To Reset Navien Tankless Water Heater?

Once you take the corrective action to fix the water heater error code, it should go away on its own. But sometimes, the error code can still stay due to a temporary glitch. In that case, resetting the water heater will make it much easier to get rid of the error code.

reset button of navien tankless water heater

In fact, a lot of people recommend resetting your water heater as your first course of action whenever you see an error code. This helps make sure that the code didn’t get triggered due to any glitch if it comes back even after resetting the water heater.

Thankfully, Navien has made the reset process incredibly easy. All you have to do is press the “Reset” button and the unit will automatically reset. If you can’t see that button on the display of your water heater, then the unit you own is a different model.

Don’t worry, the process to the reset the heater is still the same. The only difference is that the reset button, in this case, will look like a backward-pointing arrow. This is common in the newer Navien tankless units. Here’s an example of what the button should look like:

new reset button of navien tankless water heater

If you want to know more about resetting a Navien water heater in detail, feel free to check out my dedicated guide on it. You’ll also learn how to hard reset Navien water heaters and factory reset Navien combi boilers.

When Does Navien Error Code E110 Usually Occur?

As you know by now, the most frequent reason behind the E110 error code is a clogged exhaust pipe. More often than not, it happens during the extreme winter season.

naviga tankless water heater ice freezes in the openings of the exhaust pipe winter time

That’s when ice freezes in the openings of the exhaust pipe and doesn’t let the fumes go out properly. Even if the ice doesn’t get completely frozen, you’ll often see a snowy texture accumulate on the exhaust and that can also be enough to trigger the error code most often.

It can be a bit of an annoying issue and you may have to clean your exhaust multiple times in a season. I’ve seen it happen a lot and unfortunately, there’s no quick fix to that. It’s just one of the downsides of living in a place with extremely harsh cold weather.

What To Do If The Navien E110 Error Code Still Remains?

At this point, you’ve already identified the major reasons behind this error code and applied the solutions. So, the error code should go away. But life can take unexpected turns at times.

If you have the misfortune that the error code still remains even after cleaning the airways and resetting the water heater, you need to be patient. The most logical thing you can do then is to contact Navien support and tell them about the issue.

As soon as you tell them about the Error Code E110, they’ll tell you to check the exhaust. Just let them know that you’ve already done it along with the other steps.

Depending on your situation, they may ask some questions and offer more suggestions. If that doesn’t work, they’ll send a technician or even you can appoint one as long as he or she is approved by Navien.

In these extremely rare cases, what happens commonly is that the pressure sensor inside the water heater goes bad. So, it detects abnormal pressure even when there is nothing wrong with the system.

Basically, it creates a false alarm and doesn’t let your water heater work properly. But it’s hard to diagnose on your own without in-depth knowledge of Navien units. So, it’s best to bring in a qualified technician at this stage to diagnose and fix the issue.

It won’t be free but at that point, you don’t have another option if you want your heater to work. Hopefully, your problem will be fixed when an expert works on it and you’ll get hot water again.


Can you use a toothbrush to clean the air intake filter in a Navien tankless water heater?

Yes, it’s completely fine to use a toothbrush if you want to do a thorough cleaning job when maintaining the air intake filter. Just make sure that you rinse it with water and wait for it to dry before you put it back in.

Why do you need to flush the Navien tankless water heater?

As you keep using your water heater, sediments build up inside the heat exchanger as water is never 100% pure. Flushing the heat exchanger is a great way to remove those sediments and expand the lifespan of your water heater.

How do you know if the Navien tankless water heater is going through an error code?

You need to look at the display panel of your Navien unit. If you see that there’s any error code being displayed on your screen, you can be sure that something is wrong with your heater. Then, check your owner’s manual or go online to find out the solutions to the problem.

Do duct cleaners come in handy when cleaning the venting?

Yes, that’s the whole point of having them. If you are cleaning the air intake or the exhaust pipes, you can get most of the dirt out using a vacuum cleaner. But you can use a duct cleaner for the bits that remain there and remove them with a little bit of work.


So, what causes Navien tankless water heater error code E110? By now, you should be an expert on it if you’ve completed this guide. You’ll just have to clean the exhaust pipe in most cases and the issue will go away on its own.

But sometimes, you may also have to implement other fixes and reset the water heater. Only on rare occasions, you’ll have to involve a technician. If your Navien water heater makes a loud banging noise, check out my guide to find out why it happens and how you can solve it.

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