Rheem Tankless Error Codes

Troubleshooting Rheem on-demand water heaters

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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.

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 heaters are using the advanced technology and have the remote controller provided with every purchase, the diagnostics becomes simple. When the problem occurs, the error code is displayed on the LCD screen of the remote, so by understanding the meaning of the code the troubleshooting gets easier.

Rheem Error Codes Guide

I will assume that the Rheem tankless water heater was professionally installed by the licensed plumber / installer. When an error code is displayed on the remote control and before you call the service, do the following to reset the system, which might fix the issue:

  • Turn the hot water tap OFF.

  • Turn OFF the remote control.

  • Wait 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 Codes Explained

Error Code 1L

The Cause:: Lime scale 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

The Cause: The blockage in the air supply pipe or the exhaust vent, or the connection / termination is loose or not properly 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

The 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

The 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 from the above works.

emergency plumber

Error Code 14

Call the technician because the water heater is overheating.

Error Code 15

The Cause: Most of the time 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 low, is the excessive temperature of the heat exchanger.

Solution: Make sure that the hot water tap is open enough so it provides at least 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 99

Change the broken blower motor.

Error Code 65

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 solution

Not enough hot water. No hot water

The water shutoff valve and hot water tap needs 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 is the water inlet filter or fixture aerator clogged and unblock it. 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 error codes might help you to troubleshoot the problem successfully, but if you cannot solve it or you cannot find the code here, I would recommend calling the licensed service technician.

If you are calling the manufacturer have the following info ready:

  • Model and serial number

  • Contractor or business name who did the installation and service

  • Installation date

  • The info about all the performed services, including dates

  • Detail about the problem


(Photo credit to Rheem)