Rheem Tankless Water Heater Code 12 (Fixed)

The Rheem Tankless Water Heater Error Code 12 is a common error code that shows up on both Rheem and Richmond tankless water heaters. Like other fault codes on the unit, this one stops the unit from producing hot water for safety reasons and to prevent damage of the system. 

Tankless Water Heaters are a great advancement in technology when compared to the traditional tank water heater systems. They are able to deliver hot water on demand with a high level of efficiency.

But better technology often means more complexity when you run into a problem.

As the repair costs rise, as home owners, we need to continue to get more skilled at fixing more advanced problems that occur with home appliances.

In this post, we will discuss what error code 12 is and how to fix it. 

What is Rheem Tankless Water Heater Error Code 12

Error Code 12 occurs when your tankless unit cannot detect a flame. First, check that the gas valve to the unit is open that that there is gas to you home. If there is sufficient gas, the problem is that your flame rods are dirty and need to be cleaned. 

Flame Rods are located in the middle left section behind panel cover

When there is there is no flame in the tankless unit, the system shuts off for safety reasons. Without flame and gas supply turned on, the tankless system would be susceptible to damage or even a fire if there is an ignition or electrical malfunction. 

This is why the unit creates a code 12 error and shuts itself down. 

With the system shut down safely you can now begin troubleshooting steps. 

How to Fix Rheem Tankless Water Heater Code 12

To fix Error Code 12, make sure that there is gas flowing to the system by checking that all gas valves are in the open position. Once verified, open up the front panel and remove the flame rods in the middle left side of the panel. Clean the flame rods and then reinstall them. 

Step 1: Remove the Front Panel of the Rheem Tankless Water Heater Unit

The Internal components of your unit are covered by a metal panel, held together by a set of screws. Remove the screws to expose the internal parts of the unit. Make sure there is no visible damage to any of the parts.

Inside Rheem Tankless Water Heater Panel

Step 2: Shut off Power to the Unit

Every tankless unit is powered by electricity even if it uses gas for heating. Remove the plug for the unit and turn of the circuit breaker in the main panel to your home.

You will be able to tell that the power source is completely turned off because there will be no air coming out of the exhaust vents on the top of the unit.

Step 3: Shut off Water and Drain the Unit

Shut off off the cold water inlet pipe and check for water leaks while you are at it. Drain the water heater by relieving it through the vent pipe. 

Step 4: Check that there is Gas supply to the unit

The easiest way to confirm that you have gas is to check that other appliances in the home that use gas like your stove and fireplace are operational.

The tankless heater itself has a gas valve that feeds it from the gas line of the utility company. The valve will have a red handle that controls flow. Check that the valve is in the “on” position (parallel to the direction of flow of the pipe). 

Step 5: Remove and Clean Flame Rods

The flame rods are responsible for detecting that there is a flame on your Rheem tankless water heater. Over time, there can be dirt or carbon buildup on the sensors. The flame rods look like L-shaped probes or pins and are connected directly to the control board of the unit. 

To remove the flame rods, unscrew the brackets that secure them to the burner assembly panel and carefully take them out.

Flame Rod Location once panel is open. Unscrew bracket holding flame rod.

Clean the rods with a paper towel and water. If the the dirt is more grimy, you can use some rubbing alcohol or acetone to clean them.

Make sure that the flame rods are dry before reinstalling them be reattaching the bracket back onto the burner assembly panel. 

Step 6: Power Up The Unit

Once the flame rod is re-installed, turn the water back on the the system and power on the unit. Don’t forget to make sure that the thermostat is on as well.

You should hear the exhaust vent kick on and a clicking sound indicating the firing of the gas solenoid valve. 

Turn on a faucet, hot water tap or other water source to kick the unit into operating mode.

Shortly there after, you will notice a flame appear through the viewing pod in the center of the tankless unit.  

Your Water heater is Operational again.

What is Richmond Tankless Water Heater Error Code 12

Error Code 12 on Richmond tankless water heater is the same as on the Rheem Tankless Unit. This fault codes signifies that there is a flame failure and that the tankless unit cannot power up as a result. Check that there is sufficient gas pressure unit. If so, remove the flame sensors and clean them.

Final Thoughts

The Rheem Tankless Water Heater Error Code 12 occurs when the flame sensor detects there there is no flame to the unit. The system shuts down in preparation for troubleshooting.

The first thing to check is that there is Gas supply to the unit. There there is no issue with gas supply, the problem is that the flame rods are dirty. Removing them carefully and cleaning them thoroughly will resolve the fault code and get your unit back in proper working order.