15 Common Rheem Error Codes [Ultimate Guide]

Rheem is a trusted American appliance brand that is close to 100 years old. Rheem offers several water heating solutions, and this article will focus on its line of tankless water heaters. More specifically, it will focus on troubleshooting your Rheem tankless water heater and what to do when you encounter the dreaded error code.

How Do You Read a Rheem Error Code?

Error codes are never a pleasant site, but they’re designed to make your life easier. By displaying a code on your tankless heater, you, or a professional, can read the  code to understand what went wrong and how to fix it.

A Rheem tankless water heater has over 30 potential codes, and the solution will differ depending on the specific make and model of water heater that you have. The most common codes include Codes 5, 11, 13, and 29. Below, we’ll explain how to read codes on your gas heater and what you should do to rectify the situation.

How to Reset Rheem Tankless Water Heaters

After you see a code on a tankless water heater, a common first step is to reset the device. Often, resetting the gas water heater allows the device to calibrate itself properly, and then the problem will fix itself.

Before you try anything else, reset your Rheem water heater. Here’s how to do it:

  • Turn off the hot water tap
  • Turn off the device itself
  • Wait for about 20 minutes
  • Turn the device back on

This should allow the device to fully reset itself, and you might find the error code has “magically” disappeared. If not, continue reading.

How Do You Troubleshoot a Rheem Electric Water Heater – Rheem Error Codes

If you encounter an code, it will be displayed on your Rheem’s digital thermostat display. You will see a number that is flashing on the display, which will be accompanied by a beeping sound. This number indicates the  you are dealing with. You can find a full list of error codes here.

Consult the guide and see whether you have a grasp on the problem indicated by the code.

Common Rheem Error Codes

There are over 30 codes possible on Rheem devices. That being said, customers have reported a much higher frequency of certain codes, which we’ll cover here. Do note that solving each code will require a comprehensive understanding of the technical details of a tankless water heater. So, if you don’t think you are up to the task, consult a professional.

That being said, here are the most common codes and some potential fixes for each:

Error Code 00

Code 00 indicates that the water heater has been running without stopping for an hour. This code is known as the continuous combustion fault.

Here’s how to fix this issue. 

  1. Close all hot water faucets in your home
  2. Turn off you recirculation pump if your unit is connected to one.
  3. Reset the unit

These steps will get fix the fault and restore your water heater back to working condition

Error Code 05

Code 05 indicates an “Imperfect Combustion Alarm.” If you encounter this, here’s what you can do:

  • See if there is anything blocking the air vent on the device. Also, check that the vent terminal was installed properly on the device. Remove any blockage you see.
  • Check the air inlet filer and clean as required.
  • Make sure that the fan motor is operating properly.

Error Code 10

Code 10 indicates that the flame has been lost on the unit. In my experience, in most cases, it is a false flame code because when I look through the site glass, the flame is still visible.

When I can see a flame but the code displayed is Code 10, the problem is that the flame sensor is malfunctioning.  

To resolve this false flame issue, start by resetting the unit. If this doesn’t work, your next step is to check the gas valve wire connections to ensure they are secure.

The gas pressure to your water heater should range between 1.2- 3.5Kpa

Error Code 11

Error Code 11 indicates an “ignition failure.” Unfortunately, many things can cause an ignition failure. Here’s what you can do:

  • Check that the gas supply is working properly and that the gas pressure is ideal, as per the manufacturer’s recommendations.
  • Check the igniter itself to ensure it is working, including how it was wired to the device.
  • NOTE: Because these are potentially hazardous areas, don’t attempt to fix a Code 11 unless you are a professional.

Error Code 12

Code 12 signifies that the water heater does not detect a flame. I have noticed that this problem occurs when the flame rods are dirty and needs to be cleaned. 

Here are the steps to fix this issue. 

  1. Shut off power to the unit
  2. Shut off gas to the unit
  3. Open the front panel 
  4. Locate the flame rods on the front right side
  5. Remove the rod by unscrewing the brackets that secure them to the burner
  6. Clean them and screw them back into place

Error Code 13

Error Code 13 indicates “Flame rod: poor or improper combustion.” Here’s what you should do:

  • Check the air intake and exhaust venting. See whether it’s correctly installed and whether it’s functioning properly.
  • Check the flame rod itself to see whether there are defects.
  • Check the venting on the device for any blockage and clear as necessary.

Related: Rheem Error 13 – Ultimate Troubleshooting Guide

Error Code 29

Error Code 29 indicates that the “temperature is too low on the heat exchanger.” If you encounter this, here’s what you can do:

  • See if the air inlet screen is dirty and clean as necessary.
  • See if the fins on the heat exchanger are dirty and clean as necessary.

These are the most common error codes, as well as the most common fixes for said codes. However, these quick fixes will not always fix your problem. A tankless water heater is a complicated device. Often, understanding how to rectify each error code requires an understanding of how the device works as a whole and how each part works together.

Error Code 1L

Code 1L indicates that there is a limescale build-up in the unit. This error is preventable by descaling the water heater on at least once a year.

To clear this fault, you will need a pump and two hoses. One for the hot side and another for the cold side. 

Once your have your parts together, here are the steps to descale the water heater

  1. Shut off the water heater by unplugging it
  2. Shut off the hot and cold water valves
  3. Open the end caps on the valves and attach the hoses to them
  4. Fill a bucket with water and add vinegar to it. For every 5 gallons, there should be 2 gallons and 3 gallons of water
  5. Put you pump into the bucket and run it for 30-45 minutes

When this process is completed, your water will be murky, because of the limescale that has been removed. 

    More Error Codes

    As mentioned above, there are several more error codes you can potentially encounter with a Rheem tankless water heater. In a worst case scenario, you may need to replace the control board.

    The specific codes might also differ slightly depending on your specific model of Rheem. For this reason, you are best to check the owner’s manual for your device for an accurate, up-to-date list of codes.

    The most common Rheem codes are found here on Rheem’s official website (click on the first drop-down FAQ section).

    In general, here are some additional things to check in order as you evaluate the issue with your unit.

    1. Make sure that power is turned on to the unit and circuit breaker is powered on
    2. Make sure that the safety device on your unit is not activated resulting in the water heater not operating
    3. Sometimes errors are caused as a result of communication fault instead of any particular issue with a component on the unit
    4. Make sure your air inlet filter is clean

    Top Advice – Contact a Professional

    Reading through Rheem’s error code guide, you’ll notice the description for each error code is quite specific. Each refers to a technical component of the tankless water heater and a specific description of the issue. In other words, you’ll need a very in-depth knowledge of these devices to understand each error code and an even more in-depth knowledge to solve it.

    Therefore, our top advice is that you contact a professional plumber when you see an error code. Try resetting the device, and if that doesn’t fix the issue, it’s best to have a professional address the situation. Unless you have an in-depth knowledge of water heaters, you’re best to not risk making the situation worse.

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