Noritz Tankless Water Heater Troubleshooting

Noritz Tankless Water Heater Troubleshooting [Ultimate Guide]

This is a complete guide on Noritz Tankless Water Heater Troubleshooting. What I am going to describe in this article: 

  • Common problems your Noritz water heater will experience over time
  • Noritz water heater remote controller issues
  • And other water heater related problems

So, let’s get started right here. 

Table of Contents

Noritz Tankless Water Heater Troubleshooting [Ultimate Guide]

This chapter will break down every common problem of the Noritz water heater. 

1. Unit Won’t Ignite When Water Is Running

Water is running but the water heater doesn’t attempt to ignite! This problem occurs because of cross plumbing and dirty water drain valve filters.  

Here cross plumbing means when you attach the hot water lines to the cold water lines or the reverse. Consequently, it’s almost impossible for you to ignite the water heater. 

Similarly, a clogged water drain valve filter will prevent the hot water from running smoothly. In other words, you hardly ignite the water heater. 

How To Fix: 

For cross plumbing, I recommend you check both the hot and the cold water lines. If you or your plumber mistakenly install the hot water piping to the cold water lines, correct the plumbing. 

Secondly, inspect the water drain valve and its filter to see whether it gets clogged by debris or not. If there is restriction in the filter, check the steps I explained below to clean the drain valve with filter: 

  • Set the water supply valve to the off position.
  • Turn on all hot water fixtures.
  • Remove both the inlet and the outlet drain plugs from the bottom of the unit. Ensure you place a bucket right below those plugs to collect the residual water.
  • Take both the water drain valve and the filter out of your water heater. 
  • Use a brush to scrub away dirt and debris from the water drain valve and wash the valve with clean water. Don’t forget to brush up and rinse the filter as well. 
  • After cleaning the water drain valve with the filter, replace them and close the drain plugs. 
  • Close all the hot water fixtures. 
  • Open the water drain valve and verify no water is leaking from the drain plugs or the water drain valve. 

2. Unit Attempts To Ignite But Fails

You turn on your Noritz water heater and it tries to ignite but fails. It happens if there is air in the gas lines or other valves. Turns out, low gas pressure can also cause the unit to not ignite. 

How To Fix: 

First off, you need to purge the air out of the system. Fortunately, it’s simple to bleed air out of the water heater. Just follow the steps showed in the following tutorial and purge the air from the gas lines: 

If purging the air doesn’t bring any luck, you should check the gas pressure. Regarding this, it will be better to call a certified plumber to check and fix the gas pressure issue. 

3. No Hot Water When A Fixture Is Opened

Hot water is not available on your Noritz tankless water heater when a fixture is opened because of the following reasons: 

  • You don’t fully open the gas and water supply valves.
  • Water supply is cut-off.
  • You may partially open the hot water fixtures or faucets.
  • No gas is flowing to the gas meter.
  • The power button is not turned on. 

How To Fix: 

Begin with taking your eyes at the gas  valve and the water supply valve. If you open those valves partially, you will get no hot water at the fixture. To avoid this issue, open both the gas valve and water supply valve fully. 

Secondly, make sure the water is supplied to the unit. If not, check the water supply valve and turn it to the on position. Don’t hesitate to check the main water line of your house if the problem still persists. 

Thirdly, check the hot water fixtures and fully open them to get continuous or steady flow of hot water. 

Turns out, the unit requires a continuous flow of gas for proper operation. If no gas is flowing at the unit, gas meter, and tank, you will get no hot water. Fully open the gas valve and ensure the gas regulator is working properly. 

Nonetheless,  verify you turn on the power button. Many of us forget to press the power button. 

4. No Water Is Available When A Fixture Is Opened

You open a fixture but no water is flowing through it. Then, I bet the water supply is cut-off or the heater gets frozen. 

How To Fix: 

Water supply will be cut off due to the problem with the main water supply line. I recommend you check the water supply line first and call a professional if you fail to fix the issue. 

Next, no water will flow when you open the fixture if the heater or its piping gets frozen due to cold weather. 

Generally, Noritz tankless water heaters have a freeze prevention feature. It will automatically protect the unit from freezing unless the outside temperature without wind is below -4°F C. 

Keep in mind; the freeze prevention feature can’t shield the plumbing external to the unit from freezing. To protect the external plumbing, you should cover the piping with insulation, heat tape, or pipe cover. 

Now, the question is- what should I do if the heaters get frozen. Well, maintain the following tips if the heater gets frozen: 

  • Turn the power off
  • Set the gas supply valve to the off position. 
  • Open a hot water faucet and keep a small stream of hot water running. The stream of water flow should be 0.1 gallon per minute. 
  • The water flow may become unstable from time to time.
  • Check the flow 30 minutes later. 

The best bait is- drain your water heater if you are not going to use the water heater for a long period of time. It will provide the best protection against freezing. 

5. Water Takes Time To Become Hot

You turn the hot water faucet but it takes time for the water to get hot. Well, it’s not a problem at all. You should give enough time for the cold water in the pipes to drain out. 

Besides, long distance between piping and the shower can also be the culprit behind this issue. If you want to get hot water right off the bat, I recommend you install a recirculation tank between the unit and the shower. 

6. Water Is Too Hot

Scalding hot water is not expectable at all. If the water feels too hot, I bet you set the temperature to a higher setting like above 125-degree F. 

To fix this issue, I recommend you adjust the temperature to your desired setting. You can easily adjust the temperature by using the Up and the Down buttons from the controller. 

Besides, the water temperature will be too hot than the setpoint of the remote controller if the water supply temperature is high. 

Again, the water temperature will exceed the safety level if only a small amount of water is demanded. 

7. Water Is Not Hot Enough

The lower setpoint of temperature is a reason that can use the unit to not heat the water sufficiently. To fix this problem, just increase the temperature by pressing the Up button from the controller. 

Secondly, you won’t get enough hot water out of your Noritz water heater if the water temperature setting is inappropriate. 

For example, if your fixtures incorporate mixing valves, the water temperature will be less than the set temperature. In this case, you should set the temperature a bit higher than usual. 

Turns out, the output water temperature will be lower than the temperature set on the remote controller if the amount of hot water required is high. 

You should set the temperature on the remote controller approximately 20-degree F higher than the required temperature if you adjust the temp using thermostat controller water mixing valves. It will ensure the appropriate fixture temperature. 

8. Water Is Cold When Only A Fixture Is Open

Noritz Tankless Water Heater won’t heat the water if the water flow rate is less than 0.5 GPM. 

If you want to fix this issue, you should increase the flow rate. That’s why you should open more than one fixtures. It will help maximize the water flow to pass through the unit. 

And what happens next is- the unit will start heating again.  

9. Water Temperature Fluctuates

You will observe a reduction in hot water temperatures if you don’t set the temperature at 115°F to 120°F. Turns out, the water temperature will fluctuate if the water filter gets clogged by dirt and debris. 

How To Fix: 

Check the water temperature setpoint and ensure you set the water temperature between 115°F to 120°F. To adjust temperature, just use the Up and the Down buttons on the controller. 

Next, inspect the water filter and clean it if there is any restriction inside the filter. Fortunately, I broke down the water filter cleaning procedure step by step at the beginning of this guide. 

10. The Amount Of Hot Water At A Certain Fixture Is Not Constant

The amount of hot water at a certain fixture may reduce when hot water is demanded at other fixtures. On a Noritz water heater, the max flow available is 7.5 GPM at a 45°F temperature rise. 

You will get a sustained amount of hot water when the hot water demand at other fixtures will reduce. 

Besides, you will get unstable water temperature & pressure because of pressure fluctuations and other plumbing conditions. In this case, you don’t need to take any action as the temperature should stabilize after a short time. 

Therefore, some types of hot water taps discharge large volumes of hot water at first but stabilize after time. 

Lastly, the heater itself limits the amount of hot water that can flow through it to a small amount initially. But the amount will increase over time. The water heater will do this to keep the temperature stable. So, don’t worry about it. 

11. Amount Of Hot Water Available Has Decreased

Hot water available in the water heater will decrease over time if scale forms in the unit. And surprisingly, it’s normal if the supply water is hard and you don’t treat it. 

Scale formation can easily be removed by flushing the unit. To prevent the sediment from building in the water heater, you can install a water softener or scale inhibitor. 

12. Setting Temperature Can’t Rise

This problem will occur if the maximum temperature setting is not appropriate. For example, if you set the maximum temperature to 140°, you can’t raise the temperature above this. 

To fix this issue, you need to adjust the Misc Settings. Follow the below steps to enter this settings: 

  • On/off button should be off.
  • Press the Menu button inside the cover and choose Misc Settings using the Up and the Down buttons.
  • Select the ‘Max Set Temp’ using the Up and Down buttons and hit the Enter button. 
  • Finally, set the Max Set Temp using the Up and Down buttons. 

If you want to change other settings, choose the option and press the Enter button. To return to the home screen, tap on the Menu button. 

Noritz Water Heater Remote Controller Issues

Typically, you will encounter the following remote controller problems with your Noritz Water Heater. 

13. On/Off Indicator Won’t Light

If  a power failure is occured, the on/off indicator on the Noritz remote controller won’t light up. The indicator light will also not come on if you fail to connect the power properly. 

I highly recommend you call a certified electrician to fix the power failure issue. On the other hand, you can try this by yourself if you are electrically handy. 

14. Water Temperature Changes After A Power Failure

When you encounter this issue, you should reset both the temperature setting and the flow meter alarm setting after power outage. 

To reset the temperature setting, press either the Up or the Down buttons to adjust the temperature. 

Also, don’t forget to set the flow meter alarm setting. 

15. Clock Display Shows “- : – -“

This clock display will show this icon or no time will be displayed on the clock if a power failure has occurred or disconnected the power. 

To resolve this issue, you should follow the below steps I described to reset the clock: 

  • Tap on the Menu button inside the cover.
  • Ensure you choose the Set clock option on the menu.
  • Press the Enter button to access the set clock option. 
  • Now, use either the Up or the Down button to reset the clock.
  • Lastly, press the Enter button again to complete the clock setting.

16. Flow Meter Alarm Doesn’t Sound

The flow meter alarm doesn’t sound or it makes a sound before the bathtub has been filled to the set amount. 

Well, the flow meter alarm will sound before the tub is full if the hot water is used for other fixtures while filling the bathtub. So, it’s not an issue at all. 

Apart from this, the tub will fill more than the setting of the flow meter alarm if you use mixing valves or cold water is mixed with the hot water at the fixture.  

17. Setting Can’t Be Changed

You can’t change the setting if the remote controller is locked. Besides, these buttons like the PROG, MENU, and Up & Down buttons won’t work if the remote controller is locked. 

How To Fix: 

Unlocking the remote controller will help you change the setting. To unlock the remote controller, press and hold down the PROG button for approximately 2 seconds. It will bring the display to the previous screen after unlocking the remote controller. 

Other Issues

Apart from those problems I mentioned, you will also go through the issues with your water heater. 

Heater Stops Burning During Operation

The water heater will stop burning in the middle of the operation if you don’t open the gas valve or the water supply valve fully. 

So, check the position of the gas valve or the water supply valve. If they are partially opened, just open them fully. 

Not opening the hot fixtures fully can also cause the unit to stop burning during operation. Take a look at the hot fixtures and verify you open them fully. 

Don’t hesitate to call a professional if no gas is flowing at the gas meter.

White Smoke Comes Out of The Exhaust Vent

It’s normal. The white smoke you see coming out of the exhaust vent on a cold day is actually steam. In short, you don’t need to worry about it. 

Hot Water Is Turbid 

Luckily, it’s also normal as well as harmless. Small bubbles appear as the air in the water is heated and depressurized quickly to atmospheric pressure. 

Water Appears Blue 

It’s also not a problem at all. If a small trace of copper ion is contained in the water, you will notice the water turns into blue. It will not be harmful for health. You can easily avoid this issue by cleaning the bathtub or wash-basin frequently. 

A Small Amount of Water Discharges From The Pressure Relief Valve

The pressure relief valve will drip a small amount of water when the water heater is under high-pressure. Indeed, it’s normal and the water heater will do this to prevent the unit from blowing away. 


I organized this guide on Noritz Tankless Water Heater Troubleshooting with all the problems & their solutions. So, it will be 100% worth bookmarking this guide on your browser. As a result, you will get this article whenever you need it to fix a problem. 

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