Tankless Water Heater Error Codes

Service & Maintenance · Troubleshooting

Tankless Water Heater Error Codes

Step-by-step instructions when your tankless unit stops working—what to check, how to read error codes, and when to contact us.

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My Tankless Water Heater Stopped Working. What Should I Do?

Follow these steps to check your unit, record error codes, and know when to call Blue Conservation.

Step 1. Note When the Issue Started

Make note of when you first noticed the issue. Did the shower suddenly go cold, or did the temperature fluctuate? Is it happening at other fixtures? Is it intermittent, worsening over time, or a sudden failure? Keep the hot water running if it makes sense to do so.

Step 2. Check the Tankless Water Heater

Most tankless units have easy-to-read displays and will show you the hot water set temperature and display a red light, or even a flame symbol, to show the unit is active. They will also display error codes if there is an active issue within the unit. Some error codes will disappear when you turn off the hot water, since this also turns off the water heater. So, it is best to keep the hot water running and check the water heater display when you feel something might not be working properly.

How Do I Check for Error Codes?

Many of the units will flash the code in red or some will even emit a noise indicating there is an active error. Some tankless water heaters have an easy-to-view display where you can make selections and view the error history. Other units require pressing buttons on the display to enter the error code list. The user manual will have instructions to access the information.

Step 3. Write Down the Error Code

If you’re comfortable working with mechanical equipment, some common error codes can be resolved very quickly. Write down the error code and keep a log of error codes as well as issues and concerns.

Step 4. Reset or Power-Cycle the Unit

Many issues can be resolved and error codes cleared by resetting or power-cycling the unit. The easiest way is to unplug or turn off the power to the unit for at least 30 seconds and then plug it back in. Often, this rebooting of the tankless water heater’s computer system will resolve issues with the unit. Newer tankless units will keep an error code history, but it is best to keep a record of the error codes so that if it comes back or if a different code appears, you can provide this information and we can troubleshoot faster and provide repair recommendations for your system.

Step 5. If Resetting Does Not Resolve the Issue

If resetting the system does not resolve the issue, and there is no error code, it may be a plumbing problem, or an issue with the tankless unit. If there is an error code, the manufacturer lists below will assist in identifying the probable issue, but it is best to contact a trained technician.

Tankless Unit vs. General Plumbing?

If the issue is with a single fixture, like “my shower isn’t getting hot enough, but the kitchen sink is fine,” it’s likely the issue is within the shower. However, we like to confirm by reviewing the water heater. Most modern tankless systems can easily display flow rates, outgoing temperature, and incoming temperature. With this information, we can typically diagnose the issues. Blue Conservation specializes in servicing and supporting tankless water heaters. At times, a general plumber may be your best resource to resolve your issue.

Step 6. Check the User Manual

All tankless units will have a sticker on the outside of the cabinet with the manufacturer, model, and serial number. With this information, you can access the manufacturer website and download the user manual for just about any unit. You can also contact the manufacturer and determine warranty coverage and system information.

Step 7. Contact Blue Conservation

We stock parts for our most popular Rinnai and Navien units, and can easily procure parts from other manufacturers. Please have your unit information available when you text or call.

Common Tankless Water Heater and Combi-Boiler Error Codes

Most tankless units have highly sophisticated software and control modules to monitor the internal components. They typically have displays capable of communicating a wide range of fault or error codes. Most error codes can be cleared by power-cycling the unit. This is as simple as unplugging the unit for 30 seconds and then plugging it back in. When the system reactivates, the error code may clear. It is best to record and document the code and when it appears, in case further troubleshooting is needed.

Blue Conservation also recommends researching the error code to determine if a service call appointment is necessary. Members of our Blue Club can always contact us by text, phone, or email for assistance regarding error codes.

Below is a list of common error codes from the five most common manufacturers of tankless water heaters. It is not a comprehensive list. For a complete list of error codes, or codes specifically for your unit, refer to your equipment manual or check with the manufacturer.

Error codes and recommendations are for informational purposes only and are not a substitute for professional assistance.

Do not remove the cover from your system. This should only be done by a professional who has been certified by the manufacturer to conduct troubleshooting, diagnostics, and repairs.

Do not remove the cover of any tankless unit without knowledge or training of the system and components within!

Error Codes by Manufacturer

Select your equipment brand for common error codes and troubleshooting guidance.

Rinnai Error Codes

View common Rinnai tankless water heater error codes and troubleshooting recommendations.

View Rinnai codes →

Navien Error Codes

View common Navien tankless water heater error codes and troubleshooting recommendations.

View Navien codes →

Noritz Error Codes

View common Noritz tankless water heater error codes and troubleshooting recommendations.

View Noritz codes →

Rheem Error Codes

View common Rheem tankless water heater error codes and troubleshooting recommendations.

View Rheem codes →

Emergency Response

BLUE CLUB MEMBERS ALWAYS GET PRIORITY SERVICE! Let us know if you are a Blue Club member—members receive priority and expedited services. Learn about Blue Club →

If you are experiencing a boiler, combi, or tankless water heater emergency, text us right away at 484-469-0718.

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Please Include the Following Information

Name and address, including email

Equipment make and model

Description of the problem and any error codes being displayed

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Let us know if you are a Blue Club member! Members receive priority and expedited services.

Text Us With the Right Information

Have your make, model, and error code ready. Text 484-469-0718, call us, or use our contact form—and let us know if you are a Blue Club member.

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Service & Maintenance · Troubleshooting