Navien tankless water heater No hot water [✓Easy fix]

Navien tankless water heater not producing hot water? Don't worry! We have an easy fix for you. Follow our simple steps to restore hot water in no time.

Discover the excellence of Navien tankless water heaters, a top choice in the market for your hot water needs. Designed to deliver unlimited hot water on demand while requiring minimal maintenance, Navien is renowned for its long lifespan and energy efficiency.

Although Navien tankless water heaters are highly reliable, occasional issues may arise which lead to no hot water from the heater. In this comprehensive guide, “Navien Tankless Water Heater No Hot Water [✓Easy fix]” we address common issues that can arise with your Navien unit and provide simple solutions to get your hot water flowing again in no time. Whether you’re facing an error code or experiencing performance issues, our troubleshooting tips will come in handy to keep your Navien unit running smoothly.

1) No Gas and power to the unit

Ensuring Proper Electrical Connection:

One of the main reasons your Navien Tankless Water Heater may not be producing hot water is an inadequate electrical connection. Here’s what you need to do to ensure a proper electrical connection:

  1. Verify that the water heater is plugged into a 120VAC electric outlet. Check that the power cord is securely inserted into the outlet.
  2. Make sure the electric outlet is properly grounded. A grounded outlet is essential for the safe operation of the water heater. If you suspect any electrical issues, it is recommended to consult a certified electrician.
  3. Inspect the condition of the outlet. Look for any signs of damage, loose connections, or burn marks. If you notice any issues, have a professional electrician address them promptly.

Proper Gas Supply:

In addition to a reliable electrical connection, the Navien Tankless Water Heater requires the correct gas supply for ignition and heating. Follow these steps to address any gas-related issues:

  1. Check the main gas control valve located near the water heater. Ensure it is in the “On” position. If it’s turned off, the water heater will not receive gas and won’t be able to heat water.
  2. Confirm that you are using the appropriate type of gas required by your Navien Tankless Water Heater. Check the unit’s specifications or consult the manufacturer to determine the correct gas type for ignition. Using the wrong type of gas can prevent the water heater from heating water effectively.
  3. To ensure that your Navien Tankless Water Heater is receiving the appropriate gas supply pressure, consult the owner’s manual or the manufacturer’s specifications for your specific model. These resources will provide you with the recommended gas supply pressure values. To accurately measure the gas pressure, use a manometer, which is a specialized tool designed for this purpose.Refer to the table below to ensure that the gas pressure is within the manufacturer’s specified limits:
    Gas Type Minimum Pressure Maximum Pressure
    Natural 3.5 in WC 10.5 in WC
    Propane 8 in WC 13 in WC

Defective Flow Sensor

If you’re experiencing a lack of hot water from your Navien tankless water heater, the reason could be a malfunctioning flow sensor. The flow sensor plays a crucial role in monitoring the water flow rate within the system and sending this information to the PCB (Printed Circuit Board).

When the flow sensor becomes faulty or broken, it fails to provide the accurate signal to the controller. Consequently, the PCB fails to maintain the flame, resulting in your Navien Tankless Water Heater Goes Cold.

navien water heater water flow sensor location

To address this issue, start by turning off the power supply to your water heater for safety. Then, remove the front cover plate to access the flow sensor, which is typically located in the lower part of the unit above the cold water connection. Inspect the flow sensor for any debris or dirt that may be causing it to malfunction. If you find any obstructions, carefully remove the clamps from the sensor and clean it thoroughly.

However, if the flow sensor is defective or irreparably broken, it will need to be replaced to restore your water heater to normal operation. It’s important to note that replacing the flow sensor requires professional skills and knowledge. Therefore, we highly recommend contacting a qualified technician to handle the replacement process for you.

As a helpful tip, consider installing a corrosion-resistant stainless steel flow sensor. This type of sensor helps prevent rapid rust build-up and ensures the turbine can withstand high process pressure, promoting longevity and reliable performance for your Navien tankless water heater.

Blocked Water Inlet Filter

The cold inlet water filter is often to blame when there is an issue with the water flow. Over time, this filter can become clogged with dirt and minerals, hindering the proper flow of water. To ensure consistent water flow and optimal performance, it is important to periodically clean the cold inlet water filter.

Now, let’s move on to the steps on how to clean the cold inlet water filter:

  • Begin by turning off the unit using the power button on the front panel.
  • Take a plastic bucket and place it under the water heater to catch any water that comes out while draining and cleaning process.
  • Close the cold water supply valve to the water heater system. Open all the hot water faucets in your home to drain and release any pressure within the system.
  • 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.locating inlet water filter in the navien tankless heater
  • Let the water drain completely from the water heater, water may be hot so be cautious.
  • Take a close look at the cold water inlet filter and check for any clogs. Put the filter under the running tap water to clean the dust or debris, if necessary use a soft brush to scrub it.navien inlet water filter with scales and debris
  • Once the cold water inlet filter is clean 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.
  • Finally, follow the reverse order of the previous steps to refill the unit and restore the water supply.

Clogged Heat exchanger

Over time as the heater ages, mineral deposits and sediment can accumulate within the heat exchanger, restricting water flow and reducing its heating efficiency. In this comprehensive guide, we will walk you through the process of descaling and unclogging your Navien tankless water heater heat exchanger, allowing you to restore optimal hot water flow and efficiency.

Understanding the Heat Exchanger: The heat exchanger in a Navien tankless water heater is a crucial component responsible for heating the water as it passes through. However, mineral-rich water can lead to scale formation within the heat exchanger, hindering its ability to transfer heat effectively. Additionally, sediment and debris can accumulate, further obstructing water flow. Descaling and unclogging the heat exchanger is necessary to remove these deposits and restore its performance.

Materials Needed:

  • Descaling solution (compatible with tankless water heaters)(white vinegar)
  • Submersible pump
  • Bucket
  • Two Hoses
  • Wrench
  • Cleaning brush
  • Protective gloves

Descaling Process for Navien Tankless Water Heater Heat Exchanger:

  1. Turn off power and water supply.
  2. Drain the water heater completely.
  3. Prepare a descaling solution in a bucket and put the pump inside it.
  4. Connect a submersible pump and hose to the cold water inlet valve. Connect another hose to hot water outlet side and put other end of it in the bucket.
  5. Circulate the descaling solution through the heat exchanger for the recommended time.
  6. Flush the heat exchanger with clean water to remove any remaining solution and deposits.
  7. Inspect and clean the heat exchanger surfaces using a brush or cloth.
  8. Reassemble the unit and restore power and water supply.
  9. Regularly descale your Navien tankless water heater to prevent future buildup and ensure optimal performance.

For detailed explaination on how to descale navien tankless water heater along with images please check our article: Navien tankless water heater maintenance: Clean & Descale

Blocked Air intake filter

A Navien tankless water heater relies on a proper air intake system to ensure efficient and uninterrupted operation. The air intake pipe, located on the top of the heater, allows the heater to draw in the necessary air for combustion. However, over time, the air intake filter can become clogged with dirt, dust, insects, and other debris, hindering the airflow and potentially causing problems for combustion and performance issues. Regularly cleaning the air intake filter is essential to maintain the optimal functioning of your Navien tankless water heater.

how to remove air intake filter on navien tankless water heater

For detailed explaination with images refer our article on how to clean air intake filter of navien tankless water heater.

Remember to clean the air intake filter every 3 to 4 months to prevent the accumulation of dust and debris that can impede the airflow. Regular maintenance of the air intake system will help ensure the longevity and efficiency of your Navien tankless water heater.


The above listed are the main problems for no hot water from navien water heater, After following and checking the above the methods and still not able to get hot water, check for any other errors and refer our navien error codes list to solve or contact Official Navien customer support.

If our article helped please share it with your friends and if you have any doubts please comment below.

Frequently asked Questions:

Q: How can I troubleshoot a Navien Tankless Water Heater Goes Cold?
A: Start by checking the power supply and ensuring that the unit is receiving electricity. Verify that the gas supply is adequate and the gas control valve is turned on. Check the flow sensor, heat exchanger, and ignition system for any faults or obstructions.

Q: Can a dirty heat exchanger cause a lack of hot water in a Navien tankless water heater?
A: Yes, a dirty heat exchanger can impact the performance of your Navien tankless water heater and result in insufficient or no hot water. Over time, mineral deposits and scale can accumulate on the heat exchanger, reducing its efficiency. Regular maintenance, such as descaling the heat exchanger, is recommended to ensure optimal performance and uninterrupted hot water supply.

Q: What should I do if my Navien tankless water heater is not igniting?
A: If your Navien tankless water heater fails to ignite, it could be due to a variety of reasons, such as a gas supply issue, a faulty ignition system, or a blocked air intake.

Q: How often should I clean the air intake filter of my Navien tankless water heater?
A: It is recommended to clean the air intake filter of your Navien tankless water heater every 3 to 4 months.

Q: What if I have tried all the troubleshooting steps and still have no hot water?
A: If you have exhausted all troubleshooting steps and are still experiencing a lack of hot water from your Navien tankless water heater, it is best to contact a qualified technician or Navien customer support. They have the expertise to diagnose and resolve complex issues that may require professional intervention or component replacement.

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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