Rheem Tankless Error Codes
Troubleshooting guide
(updated 2017)

How to troubleshoot Rheem tankless water heaters by using the service error codes chart. Symptoms, causes and step-by-step troubleshooting guide to fix the most common problems on Rheem on-demand models. How to get help!

Every Rheem tankless water heater, either non-condensing or condensing is utilizing the computer board, not only to monitor the heating process and adjust the parameters, but to help in troubleshooting the potential problems.

Since the Rheem tankless heaters are using the electronic control board and advanced technology with an optional remote controller and control panel, the diagnostics becomes simpler. When the problem occurs, the error code is displayed on the LCD screen of the remote or user interface, so by understanding the meaning of the code the troubleshooting gets easier.

Rheem error codes guide

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We will assume that the Rheem tankless water heater was professionally installed by the licensed plumber/installer. When an error code is displayed on display and before you call the service support, do the following to reset the system, which might fix 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 nothing happens after resetting the unit and the error code is still visible do the following:

  • Close the hot water tap and turn OFF the remote.
  • Use the error code guideline below to see where the problem is, or call the licensed technician if the code is different from those found here. 

Error Code 1L

Cause: Limescale deposits in the heat exchanger... water flow is reduced, and the temperature increases significantly.

Solution: You must descale the water heater. See the example of descaling the Bosch tankless heater.

Error Code 05

Cause: The blockage in the air supply pipe or the exhaust vent, or the connection/termination is loose or not correctly done. The alarm sounds every 60 seconds when the tap is open.

Solution: If you cannot find the problem on the venting system, and cannot remove what is blocking the normal operation, call the service.

Error Code 11

Cause: The gas shut-off valve is not open completely.

Solution: Make sure that the gas shut off valve provides enough gas to the main gas burner, and there is no obstacle on its way.

Error Code 12

Cause: The water heater and its burner doesn't get enough gas.

Solution: If your tankless water heater is using natural gas, make sure that there is no interruption in gas supply from the distributor. If using the propane gas, make sure that the propane tank has enough gas.

Error Code 13

Call the service if none of the steps taken above works.

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Error Code 14

Call the technician because the water heater is overheating.

Error Code 15

Cause: Most of the time the water heater doesn't start because the hot water tap is not fully open so the water flow is low. Another problem that might occur when the water flow is reduced is the excessive temperature of the heat exchanger.

Solution: Make sure that the hot water tap is open enough, so it provides at least the minimum required water flow.

Error Code 29

Clogged condensate neutralizer. Call the technician.

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.

Common problems and solutions

Not enough hot water. No hot water

The water shutoff valve and hot water tap need to be fully open. Increase the temperature on the remote if it is set too low. If the water heater has the mixing valve installed, and it does not operate properly, it has to be replaced. Check if the water inlet filter or fixture aerator is clogged and unblock it if it is. Follow the descaling procedure to remove the scale build up in the heat exchanger (there should be an error code).

Water is not hot enough

Check the thermostat on the remote control, it might be set too low. Check the gas pressure; it might be too low, or the gas valve is not fully open.

Water too hot

Water temperature on the remote control is set too high. Water flow is too low, or the shutoff valve is not fully open.


The above list of Rheem tankless error codes might help you to troubleshoot the problem successfully, but if you cannot solve it or you cannot find the code here, or it is hard to fix the unit, I would recommend calling the professional.

If you are calling the manufacturer make sure to have the following info ready:

  • Model and serial number.
  • Contractor or business name who did the installation and service.
  • Installation date.
  • Info about all the performed services, including dates.
  • Details about the problem.
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