Navien Tankless Water Heater Humming Noise [Reasons + Solutions]

The number one reason behind Navien tankless water heater humming noise is the build-up of minerals. You can remedy this issue by descaling the heater. As a preventive measure, you should also install a water softener if you have a hard water problem.

navien tankless water heater humming noise

However, it can also happen due to the following reasons:

  • Siphoning water.
  • Loose or dirty parts.
  • Water hammering.
  • Partially closed valves.
  • Loose heat exchanger.
  • Dirty flow sensor.
  • Leaks
  • Obstruction in pipes.
  • Dirty or malfunctioning fan.

We’ll discuss all these issues in detail and how you can fix each of them in this guide. So, let’s dive right into it.

Table of Contents

Are you wondering why there’s a humming noise from the tankless water heater in your home? Don’t worry. We’ll discuss all the potential reasons behind it in this section.

Note: You can also read how to fix the navien tankless water heater leaking from the bottom.

1. Mineral Build-Up

The most common reason behind your tankless hot water heater making a humming noise is the build-up of minerals. The problem will be even more severe if you live in an area where hard water flows through the pipes.

Minerals like Calcium and Magnesium accumulate on the pipes and cause this issue. If you don’t do something about it soon enough, it can even block the heat exchanger and cause a whole new set of problems.


The sediment that has built up in your system will not go away on its own. You need to flush your system to get rid of it. You can do it using vinegar and flushing kits that you’ll find at hardware stores.

Follow these steps to descale your heater:

Step 01 – Drain Water Inside The Heater

drain water inside the heater
  • Turn off both the hot water and cold water isolation valves.
  • Release the caps from the service valves and connect the hoses to them.
  • Place a bucket on the other end of the hoses and open both service valves.
  • Keep waiting until you no longer see any water coming out from both lines.

Step 02 – Run Vinegar Through The Heater

run vinegar through the heater
  • Put two gallons of vinegar in a bucket.
  • Connect a sump pump to the cold supply line of the heater. You must use the cold side here. Connecting to the hot side will not work.
  • Make sure the pipe from the hot side is pointing to the bucket. The vinegar should go into the water heater, get recirculated, and come out through the hot side.
  • The large valves should be turned on and the service valves should be turned off.
  • Place the pump into the bucket, turn it on, and let it pump for at least 45 minutes. Then, turn off the pump.

Step 03 – Flush The Vinegar

  • Turn off both the service valves and remove the hoses connected to them.
  • Attach a regular garden hose to the hot side of the service valves.
  • Open the isolation valve on the cold side and let the water run for at least 10-15 minutes.
  • Turn off the hot side service valve again once the vinegar has been flushed out.
  • Attach the caps to the service valves that you took off when drawing water from them.
  • Turn on both the hot water and cold water valves.

Keep in mind that you must descale your water heater at least once a year. If you don’t, it can cause a lot of issues besides just the humming noise. It’s also one of the reasons why your Navien tankless water heater goes cold.

If you live in an area with hard water, you should install a water softener. It’s a great preventive measure to minimize the build-up of minerals. Besides improving the longevity of the heater, installing a water softener will also improve the quality of the water in relation to your health.

2. Siphoning Water

It’s normal for your tankless water heater to make some noise when it’s providing hot water. But if you hear it making sounds even when you’re not using it, it could be a cause of water siphoning.

As a homeowner, it’s your duty here to check the other water fixtures in your house and see if it’s happening. There must be a vacuum somewhere that drains the water from your water and causes this loud noise and vibrations.


Diagnosing whether you have this issue or not can take some time but the solution is simple. Call a plumber and have him install a check valve so that the other fixtures don’t interfere with the flow of water to the heater.

The fixtures that work with the water heater and the ones that don’t should be separated from each other with this valve. Doing so will solve this issue and get rid of the Navien water heater humming noise.

3. Loose Or Dirty Parts

Though water heaters are meant to last for a long time, they don’t last forever. With time, the components inside it can become loose. When that happens, you may find that your tankless water heater sounds like a jet engine.

inspect the parts inside the heater

It’ll also be followed by strong vibrations when something inside the heater gets loose. Your job here is to take off the front panel and try to locate what has come loose inside the heater.

Besides loose parts, dirty parts inside the heater can also create blockages and cause such sounds. Be on the lookout for them as well.


Once you find the loose components in the heater, the job is already half-done. Now, you’ll simply have to tighten them with a wrench or socket. Be careful when working on heaters as there’s always the risk of fire with them.

If you find dirty components inside your heater, give them a thorough cleaning. It’s long overdue at this point anyways. Then, check if the sound has gone away and you no longer hear the annoying Navien humming noise.

4. Water Hammering

Are you still trying to figure out why my tankless water heater makes noise? Another probable reason behind it is water hammering. It happens when there’s too much water pressure in the pipes which causes them to vibrate and bang against the walls.

water hammer arrestor

Water hammering could also be a result of the pipes being loose and not properly anchored. It usually occurs when water is turned on and off in an abrupt manner. Turning on multiple faucets at different locations of the house can also cause it as there’s a change in the direction of water flow.


The easiest solution to water hammering is to install water hammer arrestors. These devices are essentially short pieces of pipes that can relieve the pressure from the pipes.

You should also make sure that there’s enough room around the pipes for them to condensate. It’s going to be difficult to do these things on your own. So, call in a plumber to solve these problems for you.

5. Partially Closed Valves

There’s a high chance that you’ll be hearing a navien water heater squealing noise if the water valves aren’t fully open. The loud high pitch noise is created as water is pushed through a small gap. It creates a lot of pressure and voila, you have the annoying noise.

partially closed valves

So, start inspecting the valves and see if you can pinpoint where the noise is coming from. That’ll help you narrow down which valves can be causing the problem. The same thing applies to check valves and pressure relief valves.


The first solution you can try in this case is to make sure that the valves are fully open. Adjust the position of the valves and see if that solves the problem. If that doesn’t work, you’d have to replace the faulty valves.

6. Loose Heat Exchanger

Remember the part where we talked about mineral build-up causing this noise? If that doesn’t get treated in due time, they’ll eventually also affect the heat exchanger and make it dirty.

loose heat exchanger

Besides getting dirty, the heat exchanger can also get loose when it’s used for a long period. It can lead to the humming noise you hear and can even cause vibrations. When you diagnose the heater, give special attention to the heat exchanger and see if you can find any fault with it.


You already know how to descale the heat exchanger when it gets dirty. But if it has come loose, the simple solution is to tighten it. Doing these things will make the humming noise go away if the heat exchanger was causing it.

7. Dirty Flow Sensor

The flow sensor is a critical device that monitors how much gas goes into your Navien tankless water heater when it’s operated.

navien tankless water heater dirty flow sensor

If dirt or debris is present in it, the gas that’s coming to the heater will not be even. It can lead to noise.


Try cleaning the flow sensor if there’s a lot of dirt and debris in it. See if that gets rid of the noise. You’ll have to replace it if cleaning it doesn’t do the job.

8. Leaks

If there’s a leak in your system, it’ll also create a frustrating noise that should concern you. It’ll be more of a hissing sound than a humming noise. If there’s steam coming from the heater or a pipe adjacent to it, there could be a leak.

You can easily inspect if there’s a leak in the hot water line of your water heater. Turn off the cold water supply to the heater, wait for a few minutes, and turn it back on.

The water will travel at normal speed if there’s no leak and the system is working like a closed loop. But if you see the water rushing quickly toward any of the valves, it means there’s a leak.


If you’re dealing with leaks, it’s not a problem that should you take on yourself. Most leaks require the help of professional plumbers. We recommend that you do that too and have an expert solve this issue for you.

9. Obstruction In Pipes

When there is any obstruction in pipes, it can lead to restricted water flow. Hearing your navien tankless water heater buzzing with a loud- noise is a strong indicator that something is blocking the flow of water.

obstruction in pipes

Inspect your pipes and see if you can find the blockage. It’s not uncommon for rodents and insects to get in there and cause this issue. Anything washing down the drain, soap scum, or other dirt can also get in there and cause blockage in the pipes.


If blockage in pipes is the underlying issue behind the Navien tankless water heater noise in your case, you can try cleaning the blockage first. But if the pipes have gotten corroded and it’s too late, you’ll have to replace them. That should get rid of the noise.

10. Dirty Or Malfunctioning Fan

As you keep using the water heater, the blower fan inside it can get dirty. Small lizards or other insects can make their way into the tankless water heater. They can get stuck in the fan motor.

navien tankless water heater dirty Or malfunctioning fan

When these animals stay there, it obstructs the operation of the fan and causes it to become unbalanced. There will also be other debris in the fan if you don’t clean it at regular intervals. That’ll overheat the heater and eventually, it’ll start making noises.

Unplug your Navien tankless water heater and remove the front cover to inspect the fan. Even if the fan is not dirty, it can go bad with time. Pull it out and see if it spins in a smooth manner.


You’ll have to clean the fan if it’s dirty and you see dead insects or debris. Take it out by removing the screws attached to it. You can use a clean of compressed air and blow it into the fan so that it gets completely cleaned.

However, if the fan doesn’t spin properly in one direction, that means it has gone bad. In that instance, you’ll have to replace the fan.

How To Prevent Navien Tankless Water Heater From Making A Loud Noise

You won’t have to wonder why is my navien water heater making a noise if you follow the right preventive measures. There are many things you can do on your end to make sure that your heater makes little noise.

Here are some tips to help you avoid hearing the annoying humming and banging noises from your heater:

i. Use Anti-Vibration Mounts

You can reduce the noise your heater makes by a great deal if you install anti-vibration mounts. They’re usually made of neoprene or rubber and they can isolate the heater to lower the noise coming from it.

use anti-vibration mounts

If you don’t have the budget for it, there’s a small hack you can try. Place rubber or foam between the tankless heater and the walls to achieve a similar effect. You can do the same thing with loose pipes.

ii. Soundproof The Surrounding Area

One of the easiest ways to avoid the nose coming from your tankless water heater is to soundproof the area around it.

acoustic foam

Installing materials like acoustic foam or rock wool insulation will bring down the sound.

iii. Maintenance Work

The most effective method to keep the sound away and make your heater last longer is to maintain it well. Here are the things you can do to make sure that the heater doesn’t make too much noise:

  • Descale or flush your water heater at least once a year.
  • Check for loose pipes and components inside the heater every six months.
  • Install a water softener if there’s a hard water issue in your house.


Are tankless water heaters supposed to make noise?

It’s normal for them to make some noise when heating the water. But if the noise is too loud or happens when the heater is switched off, it could happen due to one of the reasons listed above.

Should the water hammering issue be immediately fixed?

If the sound doesn’t bother you, it’s not important to fix it immediately. But if you don’t solve this issue in time, the pipes and walls in your house can end up getting damaged.

Why does turning off a faucet suddenly cause water hammering?

When you turn off the water suddenly, it rushes towards the fixture and gets blocked by a closed valve. That causes the loud noise. The higher the speed of the water, the louder the noise gets on turning it off.

What causes a tapping noise in the water heater?

The most likely culprit behind it is heat traps or check valves. They ensure that water flows in the proper direction. If you can’t bear the noise, you can try replacing the heat trap with a dielectric nipple.

Can a broken washer cause a squealing noise?

Yes, a damaged washer can make a squealing noise. The ones that go bad most often are usually located near your dishwasher or washing machine.


Hearing a Navien tankless water heater humming noise can be extremely frustrating. But at least, now you know the main reasons behind it and how you can fix them.

Follow the preventive measures to make sure that you don’t face this problem in the future. Let us know what was causing the issue in your case. Drop a comment if you have any more questions about Navien tankless heaters.

About David

David is a man who loves doing research and finding out the best solution to any type of heating appliance issues like heaters and fireplaces. Whenever he finds the perfect solutions to any issues of heating appliances after doing in-depth research, he loves to share them with his readers. In fact, his aim is to help his readers to fix the issues with their heating appliances easily.More about us .

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