How To Fix Rheem Tankless Water Heater Code 11

What is code 11 on a tankless water heater? The fault code 11 on a tankless water heater (whether it’s from Rheem or Rinnai) indicates an issue with the water heater’s ignition. When there is no ignition on your tankless water heater, the error code will pop up on the control panel. 

Before heading over to troubleshoot your Rheem water heater, inspect the following things in all cases:

  • Make sure there is gas in your appliance
  • Ensure the unit is properly grounded
  • Check the gas type and gas pressure is correct
  • Bleed all air from gas lines

If all of these are okay, there are more reasons that cause your water heater to display the error code 11. For example, restricted gas flow, defective gas solenoid valves, and damaged igniter wiring are some of them. 

Fortunately, we compiled this Rheem water heater troubleshooting guide to let you learn how to fix Rheem tankless water heater code 11. So, let’s dive in. 

Table of Contents

Rheem Tankless Water Heater Code 11: The Reasons & Solutions

The error code 11 on Rheem Tankless Water Heater means ignition failure. This alert or error message will pop up on the display due to insufficient or restricted gas flow, and defective gas solenoid valves. Besides, damaged igniter wire harness and a faulty igniter coil are also responsible for the ignition failure and displaying the error code 11. 

Below, we will break down every reason that causes your water heater to pop up the error message 11. So, let’s check them out. 

01. Insufficient Or Restricted Gas Flow

Before touching anything inside your water heater, inspect your propane or gas tank first. If there is no or not enough gas in the tank, you can’t ignite your water heater. You can easily test whether there is enough fuel in the tank or not by lifting it up. If it seems light, we bet the tank is empty. 

Next, verify the gas is flowing to your burner. If the gas flow gets restricted, you can’t ignite your tankless water heater. Gas won’t flow due to closed valves or if the valve gets broken because of wear & tear. 

How To Fix: 

Bring your gas tank to your local gas station to fill it up if the tank is empty or there is not sufficient fuel in it. 

Next, check the valves are open. Make sure the red gas valve is in line with the pipe.If it’s not in line, turn it on to allow the gas to flow. Turning on your fireplace or gas stove and noticing the gas comes is another way to inspect the gas flow.

On the other hand, inspect those valves for cracks or damage if you own the heater for a long time. In this case, you need to replace the gas valve. Later in this guide, we will let you know how to replace the gas valves, till then continue to read. 

02. Defective Gas Solenoid Valves

Faulty gas solenoid valves can also be the culprit to encourage your tankless water heater to display the error code 11. If the main burner doesn’t ignite but the igniter and the fan function, understand one of the gas solenoid gas valves gets defective or there is no voltage. 

Check every inlet solenoid valve and ensure they have proper voltage. The gas inlet solenoid valve #0 should have 90-120 VDC. So, measure the voltage of connector K between Black and Yellow wires. 

Next, check the voltage of gas inlet solenoid valve #1 (connector K between Black and White wires). The voltage reading should be between 90-120 VDC. 

Then, measure the voltage of gas inlet solenoid valve #2 (connector K between Black and Red wires) and readout should be 90-120 VDC. 

And lastly, take the voltage output of gas inlet solenoid valve #3 (connector K between Black and Blue wires) and the reading should be 90-120 VDC. 

Don’t forget to check the resistance of these solenoid valves. The resistance of each solenoid valve should be 0.8 to 2.4K Ohms. 

How To Fix: 

We recommend you replace the Printed Circuit Board if any of the gas inlet solenoid valves don’t have proper voltage. It will be better to call a professional to do this task for you. 

Next, change the gas control assembly if the gas solenoid valves don’t have accurate resistance reading. This tutorial will help you learn how to replace the gas control valve. 

If those solenoid valves provide accurate voltage and resistance reading, we bet the main burner is the culprit. The following video will help you replace the burner assembly in a gas water heater. 

03. Damaged Igniter Wire Harness

A cracked or damaged igniter wire harness is also responsible for popping up the error code 11 on your tankless water heater. The igniter wiring may get damaged due to excessive wear & tear. 

How To Fix:

Visually inspect the igniter wiring for damage. You need to remove the burner cover to check the wire harness of your igniter. If you see any sign of wear and damage, you need to repair the wiring. Call a professional electrician to replace the wiring if you are not electronically inclined. 

04. Igniter Gets Defective

The water heater won’t come on if the igniter gets defective. If you are using the water heater for a decade, there is a chance the igniter gets damaged by wear & tear. Replacing the igniter is the only solution to clear the error message 11. We let you learn how to replace it in the ‘How to Fix’ section. 

How To Fix: 

Here is how you can replace the igniter on your Rheem tankless water heater: 

  • Start with unplugging the power cord. Then, turn off the gas valve, inlet water, and switch off the circuit breaker as well. 
  • Open the relief valve to let your heater drain the water. RTG20235C
  • Now, locate the igniter coil (it’s part number 4) and remove the screw that keeps it in place. Follow the igniter wiring and pull out the plastic insert. Now, remove the igniter coil. 
  • Then, grab your new igniter coil (the part number of it is RTG20235C) and install it in the place of your old igniter coil. 
  • Finally, screw up the igniter coil and put the plastic insert back into its place to complete installation. 

How To Change A Gas Valve On A Rheem Tankless Water Heater

How To Clean The Igniter On Rheem Tankless Water Heater

Before heading over to any maintenance workflows, turn off your water heater, gas flow, and the circuit breaker. 

Next, remove the burner cover from your unit by unscrewing those nuts. Then, locate the igniter and electrode of it. If you see carbon build ups or dirt on the electrode or around the igniter, clean them. 

Use a 100 grit sandpaper to gently clean the carbon buildups. Otherwise, the igniter or electrode will get damaged or go out of its position. 

How To Reset Rheem Tankless Water Heater

Rheem Tankless Water Heater has no reset button. It doesn’t mean you can’t reset this unit. To reset the unit, unplug water heater from electric outlet. Leave the tankless unit for 30 seconds. Finally, restore the power to the unit, which will automatically reset the tankless water heater.


Now, you learned Rheem tankless water heater code 11 means no ignition. You also learned your water heater will display this error code because of restricted gas flow, damaged solenoid gas valves, and defective igniter coil. 

To help you out, we provided the solution to fix those water heater issues. So, follow our troubleshooting steps to clear the error code 11 on your tankless water heater. If you have any questions about water heater problems, leave a comment below. We will be happy to help you. 

5 thoughts on “How To Fix Rheem Tankless Water Heater Code 11”

  1. My hot water heater has a very high humming noise when it runs if I slow down water flow runs ok but on full open valve humms

  2. Thank you Mr.Eric Alvarez your info on code 11 was very useful was able to solve the problem.

    • What info was shared cause I’m having the same problem

      • Hey Anthony,

        I hope you find this article helpful. Let me know whether you can resolve your issue or not by following the guideline I mentioned in this article.


Leave a Comment