Noritz Tankless Water Heater No Hot Water [Why + How To Fix]

You are experiencing Noritz tankless water heater no hot water issue due to the following reasons:

  • The power button is not on
  • Interruption in gas supply
  • Bad water flow
  • Loose or dirty ignition plug
  • Insufficient airflow

If you are not getting hot water, check whether you’ve mistakenly set the temperature too low. Turn it up. Then, open the hot water fixtures and water valves all the way to allow water to pass through the unit. The unit should begin heating again.

noritz tankless water heater no hot water

If the above effort doesn’t resolve the problem, surely there might be other issues related to gas pressure or ignition plug.

Fortunately, we have already identified all the reasons behind this heater problem with quick fixes. So, keep on reading till the end.

Noritz Tankless Water Heater No Hot Water [Why + How To Fix]

Here, we will find out the leading reasons that prevent your Noritz tankless water heater from producing enough hot water and explain their easy solutions. So, let’s scroll down…

noritz tankless water heater

1. Tripped Circuit Breaker or Power Button Is Not On

A tripped or malfunctioning circuit breaker is one of the main culprits for your tankless water heater having no hot water. If that is not the case, the best chances are power button of your water heater is not on, or you’ve plugged your unit into a non-functional electrical outlet. 

tripped circuit breaker

Mechanically, a gas or electric heater performs excellently, depending on a dedicated electrical circuit. As usual, a breaker trips for safety measures when it triggers a surge of electricity or shorted fuses. 

All that terms in the circuit hint that the current flow to your water heater was interrupted. Whatever, let’s have a look at how to fix it.

How To Fix:

First off, ensure you have plugged your water heater into a functional electrical outlet. You can test the outlet by plugging other appliances into the same outlet. Once you have confirmed, turn the power button on.

If still the problem persists, be sure it is time to inspect your circuit breaker. Open the breaker box to see if it is tripped. If so, turn the breaker off and then back ON position again. Now, just wait until your water heater heats back up.

But when your heater’s breaker trips frequently, recommend you call a certified electrician to fix this issue. 

Note: You can also read how to fix Noritz tankless water heater making a loud noise.

2. Interruption In Gas Supply

Once you have turned on the hot water faucet but have no hot water to use, an insufficient gas supply is one of the leading culprits to blame. There are a few factors that would be responsible for the interruption in gas supply. Such as:

  • Gas is being cut off by the gas meter.
  • Not enough gas in the tank
  • Gas valves are not fully opened
  • Air in the gas line
  • Obstruction in the gas lines

Above all, chances are your gas valve has broken or the gas line has leakage. This also causes the low gas to the unit that prevents to heat the water properly.

So, to ensure enough gas supply, you need to ensure a secured gas valve connection as well as resolve the other probable responsive factors. Proceed to the how-to section.

How To Fix:

First off, verify you have a fluent gas supply to your water heater. For instance, make sure you have paid your gas bill. In case, you have an LP fuel-operated tankless water heater, verify there is enough fuel in the tank. If needed, refill it. 

Investigate for any blockage in the gas supply line. After finding any blockage, shut off the gas valve and try to clear it out in order to get the heater back in working condition.

Then, inspect the gas supply valve on the unit. If it isn’t in the On position, turn the valve lever counter-clockwise to let the gas flow freely. Besides this, inspect the gas meter shut-off valve on the gas meter to ensure that it is in the On position. 

Finally, double-check the gas pressure of your water heater and adjust it to the recommended level. At times, we may suspect leakage on the valve, signing you that the gas valve has broken. 

If so, your parts need to be replaced with new ones. Don’t try DIY. Shut off your heater and call an expert plumber to handle this as an urgent case.

3. Bad Water Flow

If your tankless water heater is failing to produce enough hot water as it should, low water flow is another major factor responsible for this. You can’t expect to have hot water for your unit unless it has a minimum water flow rate of 0.5 GPM. 

too low water flow

You may face this interruption in water flow when the water supply valve to the system is not fully opened or closed at all. Or at times, the water supply is being cut off and you haven’t noticed yet. Consequently,  you can’t turn on your heater.

But that’s not the end here! There are several more factors that are responsible for water flow interruption to your water heater. Like:

  • Hot water faucets aren’t open
  • Clogged water drain valve
  • And, blocked or damaged water flow sensor

How To Fix:

To Fix the water supply issue to your water heater, here are the simple fixes that you need to apply:

i). Open The Water Supply Valves & Hot Water Fixtures

Start by inspecting the inlet water supply valves to your unit. If it isn’t open, turn the valve to the ON position and the valve lever should be  inline just like in the below picture:

open the water supply valves & hot water fixtures 

Next, make sure you have turned on all hot water fixtures fully and there are no obstructions in the faucet. Along with this, verify the water supply lines for any blockages. If so, clean it to let the water flow freely.

ii). Clean The Water Flow Sensor

Above all, unlike other tankless heaters, your water heater equips a water flow sensor that regulates the water flow to the unit and lets the fire turn on based on the flow rate. 

Clean this sensor as well. While cleaning if you find any signs of damage, be sure it is time to replace the bad sensor. 

iii). Unclog The Drain Valve

If all that fails to bring any luck to you, be sure it is time to inspect the drain valve. Like other valves in the water heater, it tends to get clogged by dirt or mineral deposits that restrict the water flow through the unit. 

Cleaning the blocked drain valve is the only solution to fix the water flow issue. For instance, locate the valve and disconnect it from the inlet for cleaning. 

Take a brush and clean the valve filter thoroughly. You can also clean it under running water and then dry it with a towel. Finally, reinstall it back into its position. 

4. Debris On The Ignition Plug

The ignition plug is one of the essential elements in a gas tankless water heater that allows the gas to flow to the ignition chamber which ignites the burner.

In case it is coated with carbon deposits, your unit won’t fire up to heat the water. As a situation, you won’t get the hot water you need even after hard trying. 

So last but not least, suspecting the ignition plug is one of the major culprits, you need to inspect this element now and fix the troubles. Here is all how you do so:

How To Fix:

Disconnect the power supply to your water heater. Remove the front access panel and locate the ignition plug from the heater inside. For instance, you can go through your water manual to locate the plug connection.

Once you have found it, look for a loose connection to the plug. Tighten the loose connection and secure it to its place. 

But in case you notice carbon deposits to the igniter plug, take 100-grit sandpaper and clean out the accumulation debris. After cleaning, replace it in its place. If needed, replace the defective ignition plug. 

5. Blockage In The Air Supply

Poor airflow is another leading reason if the burner is not igniting and you are not getting hot water from your tankless unit. The best chances are the venting of your water heater gets blocked by dirt, debris, and foreign materials that are creating air blockage in the system. 

Along with this, a clogged air filter is another major culprit for poor airflow in the unit. The filter basically helps to draw fresh air from outside for combustion and keeps the dirt out of the system.

 But in case it is blocked by dirt, debris, and lint, certainly there won’t be sufficient fresh air in the combustion chamber that interrupts the ignition process. As a result of this fact, you will not get hot water from your water heater.

How To Fix:

To ensure fluent airflow to the unit, first off you need to inspect the exhausts and air intake of your heater for any blockages. If you find clogs, remove the stuck debris using a vacuum cleaner. If needed, use a duct cleaner to clean the unreachable area. 

After cleaning the exhaust, make sure the venting system of your water heater is installed correctly.

Then,  inspect the air filter screen and clean the dirt particles using a wire brush. You can rinse it under running water. Then let the filter dry before reassembling it back in place.


How does a tankless water heater produce hot water?

Tankless water heater constantly heats water except using any storage tank. After turning on the heater, cold water flows through the heat exchanger to the unit. Then, either the gas burner or electric elements heat the water. 

How long does a tankless water heater take to supply hot water?

A tankless water heater directly heats the water to supply endless hot water. It takes about 15 seconds to reach the desired temperature. Just wait until it reaches your hot water faucets.

What ideal temperature should I set with my thermocouple?

You can set the thermocouple temperature up to 120-140ºF. But 120ºF (or 49ºC), is the ideal and recommended setting for the best performance.

How much water can a tankless water heater supply?

Normally, a tankless water heater can supply 2–5 gallons of hot water at a rate per minute. If you face a low rate of hot water, there is an issue with your water flow units/sensors.

Why is my tankless water heater getting excessively hot?

Your tankless water heater might overheat if the system doesn’t get enough cold water to absorb the heat it generates. Plus, restricted valves and insufficient air supply are responsible for being too hot.


Already, we have sorted out all the most common reasons behind your Noritz tankless water heater no hot water issue with effective fixes.  

So, whenever your Noritz tankless unit fails to deliver hot water, keep in touch with our guide to get an instant solution.

Yet, if you face any issues to fix your problems, don’t hesitate to leave feedback for us. It is our pleasure to reach out to you with a possible solution.

About Phillip

Phillip is an HVAC guy & has convenient skills in the fireplace, heater, stove & other heating systems. He has been working and writing in this field for the last 5 years. He is really passionate about writing & share his expertise through his writing to help others. More about us.

Leave a Comment