Navien Heat Exchanger Failure [Signs & Replacement Guide]

Navien heat exchanger failure is one of the most serious problems you can face with your water heater. From what I have seen over the years, I can tell you that the major reasons behind it are:

  • Installing the water heater incorrectly.
  • Not maintaining the water heater well.
  • Living in an area with a hard water supply.

I’ll talk about those issues in detail in this guide. You’ll have to replace the heat exchanger when it fails. Based on my personal experience, I’ve broken down how to replace the heat exchanger in easy steps. You’ll also know about the main symptoms of a failing heat exchanger. So, let’s dive in!

navien heat exchanger failure

One of the most common Navien complaints is a failing heat exchanger. It’s one of the main components of your water heater. So, when the heat exchanger fails, it’s terrible news as there’s no easy fix.

You’ll have to replace the heat exchanger or upgrade to a new heater. Those are the only two real options you have to deal with this issue. I’ll talk about how you can replace the heat exchanger in a later section.

For now, it’s important that you understand why a heat exchanger fails in the first place. If you can avoid making the mistakes that led to your current heat exchanger going bad, you can avoid them for the next one. So, let’s take a look at the most common reasons behind a failing heat exchanger.

01. Incorrect Installation

There’s a reason why you should always leave the installation of a water heater to an expert. If you do it yourself or hire a newbie, that opens up the possibility of making mistakes.

incorrect installation of navien tankless water heater

One thing can lead to another here and lead to a damaged heat exchanger. For example, installing a gas line of the wrong size will create more pressure on the heat exchanger. So, it can be damaged before its regular lifespan.

Screwing up the venting will also have a similar effect. I’ve seen many cases where the heat exchanger has failed because the air intake and exhaust have not been set up properly.

So, inspect if you have these issues in your water heater before you replace the heat exchanger. Then, fix those issues first. Otherwise, the new heat exchanger will also go bad soon and you’ll need a replacement part again.

02. Poor Maintenance

The main difference between heaters that last long and heaters that don’t is maintenance. If you maintain your heater, it’ll last for decades. But if you don’t maintain it properly, it’ll have all sorts of issues.

You should check the condensate trap from time to time. If it’s leaking, then identify the root cause to fix the issue. Similarly, check the air intake and the water inlet filters at least once a month. Clean them whenever they get dirty.

On top of that, it’s also important to drain your heater once in a while. Finally, you should also flush the heater at least once annually. You may even have to flush twice a year if the area where you live has a hard water supply.

I’ve gone through how you can flush your water heater in a later section. Check it out to know more about it. Also, make sure to check the venting in periodic intervals. The damage is already done to your current heat exchanger. But maintaining the new one properly will make it last longer.

03. Hard Water

Living in an area with a hard water supply is a big problem for tankless water heaters. The water inlet filter of a tankless water heater can only do so much. Eventually, the sediments will get into the heat exchanger.

As a result, the heat exchanger will start to corrode with time. Eventually, it’ll be damaged. So, you need some type of water treatment option to combat that. Installing water softeners is a common solution to fix this issue.

If you live in an area that has a hard water supply, make sure you implement this step. Otherwise, the new heat exchanger you’ve installed could also fail prematurely. So, follow the proper practices after replacing the heat exchanger.

What Are The Signs Of A Failed Navien Heat Exchanger?

There are many Navien heat exchanger failure symptoms that you can detect if you’re on the lookout for them. Let’s take a quick look at them.

01. Water Not Heating

The most obvious sign of a failing heat exchanger is that the water won’t heat. The heat exchanger is the main component that’s responsible for heating the water. When it goes bad, it can’t do that anymore.

So, the water won’t heat at all or would take a long time to heat. If it takes a long time to heat the water, it means the heat exchanger is on the verge of failure. If you don’t get any hot water at all, there’s a good chance that the water heater is damaged.

Keep in mind that the water not heating isn’t conclusive evidence that the heat exchanger is bad. There are many other potential culprits behind this issue. Make sure you rule them out before you blame the heat exchanger.

02. Leaking Water Heater

Another common sign of a cracked heat exchanger is that it’ll leak water. The water goes through the exchanger when it gets heated.

If the water leaks through the heat exchanger, it’s a dead giveaway that you have a bad heat exchanger. Remove the front panel of your water heater and check the heat exchanger. If you see any water leaking from it, you’ve found the culprit.

leaking water of navien tankless water heater

Keep in mind that a cracked heat exchanger can also lead to gas leaks. So, it’s not an issue that you should take lightly. If you have a cracked heat exchanger, get on the phone with Navien and ask for a replacement part. If you have a warranty, they’ll send it for free and you’ll have to replace it.

Apart from the heat exchanger, the water could also leak from other areas. Look for visible signs of water damage. If you see rust or corrosion on any of the internal parts, the heat exchanger may be also corroded.

03. Water Heater Is Constantly Running

When you have a bad heat exchanger, it’ll take much longer to heat the water. So, you may find the water heater running constantly when it’s damaged. If you find the heater running longer than usual, even that could be a sign of a damaged heat exchanger.

However, many other potential issues could lead to the water heater running all the time. You can check out my guide on why the Navien water heater keeps on running. Make sure you rule out the other issues to narrow down the problem to the heat exchanger.

04. Escaping Steam Or Gas

An obvious visual cue of a failed heat exchanger is to see steam escaping from your tankless water heater. The water goes through the heat exchanger when it is heated.

So, escaping steam is a sign that there’s a pinhole leak in the heat exchanger. If you notice that when operating the heater, turn it off call a technician and ask for help.

Similarly, if you notice a gas smell, that’s also a sign of a bad heat exchanger. If you feel like there could be a gas leak but you’re not entirely sure, you can get a gas leak detector. When using a combustible gas leak detector, you’d be able to take the guesswork out of the way and easily tell if gas is leaking.

05. Error Codes Pop Up

Many smart tankless units can determine what’s wrong with them. The heater fault comes up in the form of an error code. One particularly dangerous error code to look out for is the E016 error code.

error code of navien tankless water heater

It indicates that the heat exchanger is being overheated. If you see it come up in your heater, turn off the water heater for at least half an hour. Then, try to operate the heater again. Continuing to use the heater even when this code comes up can eventually damage the heat exchanger completely.

06. Boiling Sound

All the symptoms that point to a bad heat exchanger are not visual. You can also diagnose a heat exchanger by listening carefully. If you can hear a boiling sound as you go near your water heater, it signals a bad heat exchanger.

How To Replace Navien Heat Exchanger?

Replacing the heat exchanger on your Navien tankless water heater is a complicated job. But don’t worry, you’re in good hands as I know how to do it from my own experience.

Keep in mind that you’ll have to remove a lot of connections and reconnect them when replacing the heater exchanger. I’ve broken down this process into simple steps. You can follow them to carry out this job:

Step 01 – Disassemble The Unit

Start by turning off the power to the water and unplugging it from the power outlet. Then, remove the screws holding the front cover in place. Take out the front cover of the heater so that you have eyes on the internal components.

dissasemble the unit of navien tankless water heater

Then, you’ll have to drain the water from the water heater. If you don’t know how to do it, I have a guide on maintaining a Navien tankless water heater. You’ll find a section on draining the water heater in that guide.

Now, it’s time to remove the connections of the heat exchanger one by one. I like starting from the top as it makes it easy to keep track of things. Remove the flame rod connections and the wiring connections that lead to the heat exchanger.

You’d also have to undo the screw below the blower motor and remove the pope connections. As you disassemble the unit, you’ll come across the water valve. It’s common for them to leak. So, tighten the screws on those valves while you’re doing this replacement job.

Remove the freeze-protection warmers as well. If your water heater has a built-in circulation pump, you won’t have the freeze-protection warmers. Those heat exchangers are easier to remove.

As you remove the parts, make sure you set the screws aside properly. Keep the screws of the different units arranged in different groups.

You’ll have an easier time putting the heater together correctly when replacing the heat exchanger if you do that. Eventually, you’ll have to remove the fan assembly of the water heater.

Step 02 – Remove The Heat Exchanger

Once you remove all the connections attached to the heat exchanger, you’re ready to remove it. Undo the screws holding the heat exchanger in place. Some of the screws of the heat exchanger are deep.

You’ll need a magnetized screwdriver to remove them. Otherwise, you won’t be able to get a good hold of them and access them. Once you remove all the screws, the heat exchanger will get loose and you’ll be able to pull it out.

removed heat exchanger of navien tankless water heater

Step 03 – Install The New Heat Exchanger

The new heat exchanger will come with a flopper to prevent Carbon Monoxide leaks from your water heater. Apply some grease to the rubber part of the water heater and attach it to the heat exchanger.

Make sure you apply some grease to the rubber seal on top of the heat exchanger as well. It’s a good practice to lubricate the rubber components as it makes them last longer.

From here on, it’s a simple process of putting the new heat exchanger inside the water heater and reverse engineering the previous steps. So, tighten the screws you removed earlier when taking off the heat exchanger one by one.

Then, tighten all the connections you removed. A new heat exchanger will have things like ignition rods and water flow sensors already installed in them. So, you won’t have to use those parts from your old water heater.

Make sure you reattach the connections tightly. Whenever you see any rubber part, lubricate it a little bit so that it stays in good connection. Once you’re done putting all the connections back together, you’re done. You can then restore the power to the water heater and use it.

So, that’s how you can replace the heat exchanger on your own. If you feel uncomfortable doing it yourself or you lack the expertise, there’s no reason to do it. Only someone who knows his way around the tankless water heater should attempt such a job.

Replacing the heat exchanger is one of the hardest tasks you can take on as a DIYer. So, it’s better to leave it to the expert. With that said, you can save the labor charges if you do it yourself.

So, if the steps I shared are clear to you and you have the tools and expertise, you can do it yourself. Also keep in mind that if your tankless unit is old and past the warranty period, it may make more sense to upgrade to a new heater.

If you think in the long run, upgrading the heater altogether could be the most cost-efficient option. I suggest that you consider all those things before replacing the heat exchanger. If you think replacing the heat exchanger is the right choice, then carry on with the job.

How Long Is The Navien Heat Exchanger Warranty?

The warranty period on the Navien tankless water heater varies depending on the type of water heater. When it comes to the residential heaters of the NR & NP series, the heat exchanger has a warranty of 15 years.

On top of that, you’ll also get a 5-year warranty on the other parts. For The NR & NP heaters that are used commercially or for residential space heating, the warranty period is lower. You’ll get a 3-year warranty on the parts and a 10-year warranty on the heat exchanger.

The warranty becomes active from the date of purchase if you registered it properly. If you claim the warranty, Navien will send the part to you. But you’ll have to take care of the labor charges. That’s why it’s important to know how to replace the heat exchanger on your own.

However, Navien does include the labor allowance for their heaters only for the first year of use. So, if anything goes wrong in your heater by that time, you could get lucky. It still depends on the sole discretion of Navien if they want to allow the labor charges to be transferred to them.

If the heater has changed ownership over the years, there’s no need to panic. The ownership is transferable as long as the heater remains in the same location. If the heater is moved to a new location that’s different from the registered address, the warranty will become null and void.

Many other things can make the warranty void in Navien tankless water heaters. The most common ones are:

Step 01: Failure to install or use the product according to the instructions of the manufacturer.

Step 02: Using gas lines, combustible air openings, venting connections, wiring, or fusing of the improper size.

Step 03: Damage caused to the water heater after removing any parts or using any replacement parts that have not been approved by Navien.

Step 04: When the heater is damaged due to acts of god like freezing, fire, flood, lightning, or other natural disasters.

Step 05: Damage to the water heater over a long period by using water of poor quality that’ll lead to sediment build-up in the heat exchanger.

Step 06: When the rating plate of the water heater is removed by a person who is not authorized to do it.

How To Maintain Navien Tankless Water Heater?

You need to do the following maintenance tasks on your water heater to make sure that it has a long lifespan:

  • Clean it from time to time.
  • Drain the water heater.
  • Clean the water inlet and recirculation inlet filter.
  • Clean the air intake filter.
  • Flush the heat exchanger.
  • Protect the water heater from freezing.

I’ve talked about all these things in detail in my Navien water heater maintenance guide. You can visit it to learn more about all of them in detail. But, I’ll briefly go over the flushing instructions so that you can clean your heat exchanger and prevent it from getting damaged.

How To Flush Navien Heat Exchanger?

Flushing the heat exchanger is a lengthy but simple process. I’ll try to break down this process as simply as I can. Hopefully, you’ll find it easy to follow. Before getting into how you can do it, you’ll require a few things to flush the heat exchanger. They are:

  • A 5-gallon bucket. (Larger is fine but not smaller).
  • A cleaning solution. (You can use vinegar here).
  • At least 3 hoses.
  • A water recirculation pump.
flushing of navien tankless water heater

If you don’t have the water recirculation pump and hoses, you can purchase a water heater flush kit. You’ll find everything you need there. Once you get your hands on them, you can follow these steps to flush the heat exchanger:

Step 01 – Setting Up The Equipment

Press the power button of the heater to turn it off. Then, disconnect the heater from the power supply as an added layer of safety. Close both the water inlet and water outlet valves at the bottom of your water heater.

Connect one end of the hose to the valve beside the hot water line and leave the other end on the bucket. Take another hose and connect one end of it to the cold water line. Connect the other end of the hose to the outlet line of the circulation pump.

Then, the third hose will come into play. Connect one end of it to the circulation pump inlet and leave the other end free in the bucket.

Step 02 – Circulating The Solution To The Heat Exchanger

Place the cleaning solution in the bucket and open the valves “A” and “B” at the water heater. Turn on the circulation pump as well so that it can circulate the cleaning solution to the water heater.

Leave it on for at least 45 minutes to an hour so that it’s circulated properly. If you don’t have a cleaning solution, you can also use 4 gallons of food-grade white vinegar or critic acid pail. As long as you use something to do a thorough cleaning job, you’ll be fine. After that, you can turn off the pump.

Step 03 – Rinse The Cleaning Solution

Remove the free end of the drain tube from the bucket. Close the service valves and open the shutoff valves. Let the water run through the heater for at least 5-10 minutes.

Disconnect all the hoses. Take out the cold water inlet filter while you’re at it and clean it if needed. Then, place it back and make sure it’s tight. Then, you can restore the power supply to the water heater and continue to operate it.

Did Navien Recall Water Heaters Due To Faulty Parts?

Once in a while, companies tend to mess up their products during manufacturing. Sadly, Navien is no exception to that. They also have their fair share of mistakes.

The first major blunder that Navien made was way back in 2011. They had to recall around 13,000 units on December 27, 2011. The main issue in those water heaters was that the connection of the vent collar was unstable.

It may not seem like a big deal on the surface but the results from it can be catastrophic. If the vent collar got detached due to high pressure, the end user would be a serious risk of Carbon Monoxide poisoning.

CO has been given the name of an invisible killer as you can’t see or smell it. It’s extremely dangerous and causes about 400 deaths every year. So, the Navien heaters had to be recalled for the safety of the customers.

The majority of those water heaters were manufactured in 2008. CR-180(A), CC-240(A), CR-240(A), CC-180(A), CC-210(A) and CR-210(A) are the units that have been recalled. Navien replaced the Nylon 66 vent collar with PVC collars to fix this issue.

Thankfully, no injuries were reported as a result of this mistake by Navien. The majority of those faulty heaters were sold between 2008 and 2009. The customers who had already bought it were instructed to appoint a technician to fix it.

Unfortunately, the 2011 recall of Navien water heaters wasn’t an isolated incident. Navien also recalled about 3400 units on December 20, 2018, to protect the end users from CO poisoning.

The main issue in those water heaters is that the kit Navien used to convert NG to LP was faulty. The faulty units that Navien recalled were made between July 9, 2018, through October 14, 2018.

Navein has been lucky that there were no serious injuries reported even from these heaters. The NPE-180A, NPE-180S, and NCB-180E models of Navien combination boilers and water heaters were the ones that were recalled.

How Do I Reset My Navien Water Heater?

Resetting a Navien water heater is one of the most simple tasks you’ll ever come across. In most Navien heaters, you’d see a reset button on the water heater. All you have to do is press it and the heater will reset it on its own.

The reset button on most Navien water heaters is very easy to spot. That’s because it’ll have the word “RESET” written on it. But there are also some heaters where you may not directly spot the reset button.

For example, the reset button looks like a backward-pointing arrow in some water heaters. Here’s an example of what I am talking about:

reset button of navien tankless water heater

So, you’d have to identify the reset button for your water heater to use it properly. If you’re having trouble finding it, you can look at the manual to learn how to reset the heater.

If the reset button isn’t working for any reason, you can turn off the water heater and remove the electrical power connection. Then, reconnect the water heater to the power outlet and turn it on again.

I also have a dedicated guide on solving the most common Navien tankless water heater reset problems. If you’re facing any other issues when resetting your heater, feel free to check it out.


How long do Navien tankless water heaters last?

Like all other types of water heaters, tankless water heaters also require maintenance. But if you take good care of them, Navien tankless water heaters can last somewhere between 15-20 years.

Do all Navien tankless water heaters need a condensate drain?

Navien makes both condensing and non-condensing water heaters. A condensate drain is required only in a condensing unit. It’s important to remove the condensation from the water heater to prevent the water heater from facing any problems.

How long do Navien boilers last?

Navien boilers also have a similar lifespan to the tankless water heaters. They can also last for 15-20 years if you take good care of them. In some cases, they can even last longer than that.

What to do if an error code pops up after replacing the Navien heat exchanger?

If you see an error code after changing the heat exchanger, it means you’ve messed up somewhere during the installation job. You need to check your work again and reinstall the heat exchanger correctly.

Why is there water inside the air intake of my Navien tankless water heater?

If the heat exchanger is leaking, sometimes the water can shoot out of the air intake. So, you’d see water inside the air intake of your water heater. The solution is to replace the heat exchanger in that case.


Navien heat exchanger failure is a serious problem for sure. But I’ve told you everything you need about diagnosing and fixing the issue. Replacing the heat exchanger isn’t something everyone can do by themselves.

If your unit is under warranty, I’d recommend using it after changing the heat exchanger. But if it’s passed that period, you’re better off getting a new water heater. Feel free to check out my guide on why Navien water heater exhaust smells like gas in case you’re facing that issue.

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