Noritz Code 12

How To Fix Noritz Code 12?

Noritz Error Code 12 means flame loss or weak flame. This happens when your unit doesn’t get sufficient gas supply or you improperly vent the unit. Turns out, if you live in an earthquake prone area like California, a tripped earthquake shut-off valve will cause the code 12. 

Throughout this troubleshooting guide, I will walk you through every troubleshooting step to fix the issues responsible for the code 12. So, stay in tune with me till the end. 

Table of Contents

Noritz Code 12: What Does It Mean?

Flame loss or weak flame is what the error code 12 on Noritz stands for. In simple words, your tankless water heater senses a flame but it gets extinguished during operation. 

All the reasons responsible for Noritz Code 11 can be applied to the trouble code 12. In specific words, gas supply issue, dirty ignition rod, and improper inlet gas pressure are also accounting for the error code 12. 

So, I recommend you follow the troubleshooting steps I mentioned in the Noritz Error Code 11 guide to fix the flame loss issue. 

Additionally, improper venting, inlet gas pressure issue (though I discussed this in the previous guide), and tripped earthquake shut-off valve can throw the error code 12. And below, I will break down each of these issues. 

1. Improper Venting

If you own a direct vented water heater like NR83DVC, venting the water heater incorrectly can cause the unit to throw the error code 12. 

For example, the NR83DVC model from Noritz requires the use of Concentric Venting. If you don’t use this venting for this specific model, the unit will pop up the trouble code 12. 

Turns out, this concentric venting has o-rings on the smaller 3” exhaust venting. If these 0-rings are missing, the unit fails to prevent the 3” exhaust venting from leaking into the air intake side. 

As a result, it will cause the unit to throw the error code 12 or make unusual noises. 

How To Fix: 

Check the manual and ensure you use the right of venting for your specific Noritz model. If you have the NR83DVC model, you must use the concentric venting. 

Furthermore, make sure there are 0-rings on the 3” exhaust venting if you use the concentric venting. If not, re-install new o-rings. If you need further assistance, call the Noritz Support Team at 866-766-7489. 

2. Improper Inlet Gas Pressure

A proper operating tankless water heater should have the inlet gas pressure between 4” WC (min) to 10.5” WC (max). If the gas pressure goes out of range, it will cause the unit to flash the trouble code 12. 

How To Fix: 

First off, check the inlet gas pressure. In this case, you need a digital manometer to measure the inlet gas pressure. Then, watch the following tutorial to learn how to check the gas pressure: 

You must perform 3 different tests like the static test (no gas is being used), dynamic test (gas is being used), and max dynamic test (gas is being used at the unit and other gas appliances. 

Under every test, the inlet gas pressure to the unit should always stay above the minimum required gas pressure. 

If the gas pressure drops down the minimum specification, ensure: 

  • You fully turn on the gas valve
  • Size up the gas meter for the unit and other gas appliances in the building properly
  • Size up the gas line properly

3. Earthquake Shut-off Valve Gets Tripped

This is not applicable for every state in the USA. It can be only applied if you live in California. The earthquake shut-off valve will get tripped during an earthquake or other vibration. 

How To Fix: 

Just check the position of the earthquake shut-off valve on the gas line near the meter. If it gets tripped, follow the procedure to reset it labeled on the device. 

How Do I Fix Noritz Trouble Code 12?

You can reset the error code 12 from the unit by following the below steps: 

  • Verify the reasons that cause the unit to pop up the error code 12. I already discussed how to do that. 
  • Once you determine the reasons behind the code 12, resolve the issue. 
  • Reset the water heater

Check this article on Noritz Tankless Water Heater Reset Button if you don’t know how to reset the unit. 


How do you troubleshoot a Noritz water heater?

This how you can troubleshoot your Noritz Water Heater:

  • Ensure you get both the electric supply and the gas supply to the unit.
  • Inspect the air screen filter and ensure it doesn’t get filthy with dirt, debris, or lint. 
  • Check if the water drain valve filter gets clogged. 
  • Inspect the exhaust vent for blockage. 
  • Ensure you fully open up the gas valve on the unit. 
  • Make sure the gas supply at the gas meter doesn’t get cut off. 
  • Check the internal parts like burner, flame sensing rod, and the wiring. 
  • Take a look at the heat exchanger and ensure it doesn’t get clogged.

Can I unplug my water heater to reset it?

Yes, you can unplug your water heater to reset it. Indeed, this unplugging method is applicable for almost every tankless unit when it comes to resetting the water heater. 

How long does it take for a water heater to reset?

It takes only 30 seconds for a water heater to reset. Just unplug the unit, wait 30 seconds, and plug the unit into the electric outlet. It will reset the water heater. 


To sum up, it’s simple to reset the error code 11 if you can determine the reasons behind this issue. Fortunately, I make the process easy for you to discover the culprits that cause the unit to pop up the error code 11. So, what you need to do next is just follow the steps I mentioned and get your unit ready to function properly. 

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