Rheem Tankless Error Codes: DIY Troubleshooting guide and Repair Tips

Rheem tankless water heaters are renowned for their energy efficiency and continuous hot water supply. However, as with any intricate system, occasional problems may arise that demand your attention.

When an error code appears on your Rheem tankless water heater, it serves as a clear indicator that some action is needed.

Rheem tankless water heater
Rheem tankless water heater (photo: amazon.com)

These error codes are specifically designed to offer diagnostic information, making it easier for homeowners to identify and resolve issues promptly.

Whether you’re encountering challenges with water flow, gas supply, ignition, temperature fluctuations, or any other tankless problem, this guide will provide you with the necessary knowledge and meanings of the most common Rheem tankless error codes. By following the step-by-step troubleshooting instructions provided here, you can save both time and money by avoiding unnecessary repairs.

It is important to keep in mind that while some issues can be resolved through simple maintenance tasks, others may require the expertise of a professional repair service.

Every Rheem tankless water heater, whether it’s non-condensing or condensing, relies on a computer board to oversee the heating process, make parameter adjustments, and aid in the diagnosis of potential issues.

Thanks to the implementation of an electronic control board and advanced technology, including the availability of an optional remote controller and control panel, the diagnostic process is streamlined and more straightforward for Rheem tankless heaters.

In the event of a problem, the error code is conveniently displayed on the LCD screen of the remote or user interface. By understanding the significance of these error codes, troubleshooting becomes significantly more manageable.

List of Rheem Tankless Error Codes and Repair Tips

We will assume that your Rheem tankless water heater was professionally installed by a licensed plumber/installer. If an error code appears on the screen, there are a few steps you can take before reaching out to service support. Following these steps may help reset the system and potentially resolve the issue:

  • Turn the hot water tap OFF.
  • Turn OFF the remote control.
  • Wait for approximately 5 minutes.
  • Turn the unit ON.
  • Open the hot water faucet.

If, after performing the reset and the error code remains visible without any changes, please proceed with the following steps:

  • Close the hot water tap and turn OFF the remote.
  • Consult the error code guideline provided below to identify the problem. If the code differs from those listed here, it is advisable to contact a licensed technician for further assistance.

Error Code 1L

Cause: Limescale deposits in the heat exchanger lead to reduced water flow and a significant increase in temperature.

Solution: To address this issue, it is necessary to descale the water heater. Here is an example of how to descale a Bosch tankless heater.

Error Code 05

Cause: The air supply pipe, exhaust vent, or their connections/terminations may be obstructed or improperly installed. An audible alarm sounds every 60 seconds when a tap is open.

Solution: If you are unable to identify the issue within the venting system or remove any obstruction hindering normal operation, it is recommended to call the service.

Error Code 11

Cause: The gas shutoff valve is not fully open.

Solution: Ensure that the gas shutoff valve is fully open, allowing sufficient gas flow to the main gas burner, and check for any obstructions that may be impeding the gas supply.

Error Code 12

Cause: Insufficient gas supply to the water heater and burner.

Solution: If your tankless water heater operates on natural gas, ensure there are no interruptions in the gas supply from the distributor. If using propane gas, ensure that the propane tank has an adequate amount of gas available.

Error Code 13

If none of the steps mentioned above resolve the issue, it is recommended to contact the service for further assistance.

Error Code 14

Contact a technician immediately if your water heater is experiencing overheating.

Error Code 15

Cause: In many instances, the water heater fails to start due to the hot water tap not being fully open, resulting in low water flow. Another potential issue that can arise from reduced water flow is the heat exchanger reaching excessive temperatures.

Solution: Ensure that the hot water tap is opened to an extent that provides the minimum required water flow.

Error Code 29

Cause: The condensate neutralizer is clogged.

Solution: It is necessary to contact a technician for assistance in resolving this issue.

Error Code 31

Change the faulty inlet thermistor.

Error Code 33

Change the faulty outlet thermistor.

Error Code 61 or 69

Change the broken blower motor.

Error Code 65

An issue with the water flow solenoid.

Error Code 92

The neutralizer needs to be replaced soon.

Error Code 93

The neutralizer must be replaced.

Error Code P1

Water flow is below the minimum required. Increase the flow.

Rheem Tankless Water Heaters: Common Problems and Solutions

Problem: Not Enough Hot Water or No Hot Water

Ensure that both the water shutoff valve and the hot water tap are fully open. If the temperature setting on the remote is too low, increase it as needed. In the case of a water heater equipped with a mixing valve that is not functioning properly, it may be necessary to replace the valve. Check for any clogs in the water inlet filter or fixture aerator, and if found, clear the blockage. If there is scale build-up in the heat exchanger (indicated by an error code), follow the descaling procedure to remove the scale.

Problem: Water Is Not Hot Enough

Check the thermostat setting on the remote control; it may be set too low. Additionally, verify the gas pressure to ensure it is not too low, and ensure that the gas valve is fully open.

Water Too Hot

The water temperature setting on the remote control is set too high. Check if the water flow is too low or if the shutoff valve is not fully open.


While the provided list of Rheem tankless error codes can be helpful in effectively troubleshooting the issue, there may be instances where you are unable to resolve the problem, cannot find the exact error code mentioned, or encounter difficulties in fixing the unit. In such cases, it is highly recommended to seek professional assistance to ensure a proper resolution.

When contacting the manufacturer for support, ensure that you have the following information readily available:

  • Model and serial number of the water heater.
  • Contractor or business name responsible for the installation and service.
  • Installation date of the unit.
  • Details regarding any previously performed services, including dates.
  • Provide comprehensive information about the problem you are experiencing.

Related Articles

Similar Posts