Navien Tankless Water Heater Humming Noise

Navien Tankless Water Heater Humming Noise [Fixed]

Your Navien Tankless Water Heater will make a humming noise due to the following reasons:

  • Dirty heat exchanger
  • Mounting issue
  • Fan motor or motor mount comes loose
  • Loose metal enclosure cover
  • Sound may come out of the recirculation pump
  • Condensate pump is not emptying properly

To stop the humming noise, you must fix those issues. And this troubleshooting guide will walk you through the step-by-step guide to solve the issues.

So, keep reading.

Table of Contents

Why Is My Navien Tankless Water Heater Making A Humming Noise?

This chapter will disclose the reasons that cause your water heater to make a humming noise. 

01. Dirty Heat Exchanger

A tankless unit can make a humming noise for several reasons. Among them, a dirty heat exchanger is one of them. 

Over time, mineral deposits coming with the supply water form a buildup on the heating exchanger. As a result, this water heater component fails to exchange the heat and causes the unit to make a hum. 

The worst part is- your Navien tankless unit won’t heat the water if the heat exchanger gets clogged by scale or mineral deposits. 

How To Fix: 

Professionals recommend to descale or flush a tankless water heater every year. However, you should flush the unit every six months if the water is excessively hard or you run the unit at a higher temperature setting. 

Flushing the unit regularly will help avoid improper water heater operation like whining noise coming out of the unit or getting no hot water. 

To flush a tankless unit, ensure you have the following flushing kits at your fingertips: 

  • A 5-gallon capacity plastic bucket
  • Two garden hoses
  • Distilled vinegar
  • A circulation pump

Then, follow the step-by-step flushing procedure described in this article on Navien Tankless Water Heater Maintenance

02. Mounting Issue

Yes, mounting issues can also cause the unit to make a humming noise. If you or your installer fails to mount the water heater properly like not tightening up every screw, it will create a popping noise. When you turn the unit on, your heater will vibrate and it will also cause other loosening parts to vibrate. 

How To Fix: 

You may need to take apart the entire assembly. Then, install the water heater again. This time make sure you tighten up every connection or screw securely. If you are not comfortable with this task, you can call a plumber to do it for you. 

03. Motor or Motor Mount Is Loose

Every Navien tankless water heater has a blower fan inside the unit to blow away air for proper combustion. If the fan motor or motor mount comes loose from its place, it will rub against other metal parts when you turn on the unit. Consequently, it will make a humming noise. 

How To Fix: 

Just tighten up the fan motor mounting and it will stop the buzzing noise. Regarding this, turn the unit off and remove the front cover panel. Then, locate the blower fan and ensure its screw or mounting bracket doesn’t come loose. If yes, just secure the mounting bracket by tightening up the screw so that it holds the fan motor or the motor mounting securely. 

04. Loose Metal Enclosure Cover

Loose metal enclosure cover can also be a source of the buzzing noise of a tankless water heater. If the plumber doesn’t install the metal enclosure cover correctly, it will cause your water heater to resonate and rumble. 

Turns out, ensure the gaskets between the metal enclosure cover and the screw are in good condition. If the gaskets get deteriorated, you will hear the whistle when you turn on your water heater. 

Nonetheless, not sealing the piping of your water heater can also make the unit rattle. 

How To Fix: 

First off, ensure the metal enclosure cover of the unit is tight enough. If not, tighten up all the four screws that hold the cover in its place. 

Before tightening up the screws, don’t forget to check the gasket’s condition. If needed, replace the gaskets. Then, tighten up the screws to secure the metal enclosure cover. 

Lastly, make sure your plumber seals every piping. Otherwise, the vibration from the water heater operation will travel through each piping and cause the unit to whistle. If needed, hire a certified plumber to reseal every piping. 

05. Sound May Come From Recirculation Pump

The rattling or whistling noise you hear can also come from the recirculation pump of your Navien tankless unit. Generally, the recirculation pump will make a popping noise due to the following reasons: 

  • Wrong size primary loop
  • Not purging the air out of the recirculation pump
  • Mounting the pump improperly 
  • Foreign materials getting into the recirculation pump

Fortunately, I broke down each of the culprits in this article: Navien Recirculation Pump Noise. So, check that article and learn how to stop the humming noise coming out of the recirculation pump. 

06. Condensate Trap Is Not Emptying Properly

Condensate trap is filling with water but not emptying properly! If it’s the case, the water heater will make a lot of noise when the condensate trap is partially full of water. 

How To Fix: 

If you are mechanically inclined, inspect the condensate trap. I highly suggest you check the condensate drain line, whether the line is level or not, and ensure it doesn’t get clogged. Release the blockage from the drain line to let the water flow out of the drain line without any problem.


Why is my Navien Tankless Water Heater not working? 

Your Navien Tankless Water Heater won’t work due to the following reasons:

  • Plug the unit into an improper grounded electric outlet
  • Bad PCB
  • Clogged air inlet filter
  • Dirty heat exchanger 
  • Bad flow sensor
  • Dirty igniter 
  • Clogged cold water inlet filter

How do I reduce the noise on my tankless water heater?

You can reduce the noise on your tankless water heater by taking the following corrective actions: 

  • Ensure there is no loosening part. If yes, tighten up the specific component.
  • Inspect the blower fan for insect or spider wires and clean them. 
  • Don’t forget to check the pressure relief valve as sometime you may hear a tea-kettle noise from it if it’s partially open. 
  • Flush the heat exchanger with vinegar one or two times per year depending on the supply water conditions.
  • You can try out anti-vibration mounts to install the water heater to reduce the whining noise. 
  • Inspect the flow sensor and clean it if needed. 
  • Check the air intake filter for debris or dirt buildup and clean filter. I highly recommend you clean the air intake filter every 3-4 months.

How much noise does a tankless water heater make?

A tankless water heater, especially the gas-operated one, can make a noise of less than 90 decibels.  


I described all the reasons that cause your Navien Tankless Water Heater to make a humming noise. What you need to do now is- follow the troubleshooting steps I mentioned to stop the buzzing noise. 

The best suggestion for you is- maintain your Navien Tankless Water Heater routinely. This maintenance workflow includes from tightening up the loosen parts to flushing the heat exchanger. Maintaining the unit regularly will keep your tankless water in its tip-top condition for years. 

If you don’t know how to maintain the Navien Tankless Water Heater, you can check out this article. 

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