rheem tankless water heater code 11

How To Fix Rheem Tankless Water Heater Code 11?

Rheem Tankless Water Heater Code 11 means ignition failure or a problem with the ignition sensor. Here are the troubleshooting steps you should follow to reset the error code 11: 

  • Check the igniter coil first. If it gets defective, replace it with a new one.
  • Inspect the igniter and its wiring. If the igniter wire connection comes loose, tighten it up. Don’t hesitate to replace the igniter itself if it’s at fault.
  • Verify that the unit gets sufficient gas supply to the burner chamber. Also, open the gas valve fully to let the gas flow freely. 
  • Ensure you get sufficient gas supply to the unit at the right pressure. The inlet gas pressure should be between 4″ WC and 10.5″ WC for tankless water heaters fueled with natural gas. Otherwise, the allowable inlet gas pressure range is 8″ WC-13″ WC for a tankless unit powered with propane.
  • Replace the gas valve if the solenoid gas valves are at fault.
  • Check the igniter wire harness for a sign of visual damage and replace it if needed.
  • Verify that the ventilation system or exhaust is free from blockage.
  • Clean the flame rod or replace it if it gets cracked.

Table of Contents

How To Fix Rheem Tankless Water Heater Code 11: 7+ Easy Solutions

Here is the table that summarizes the mean reasons behind Rheem Tankless Water Heater Code 11, along with the corresponding solutions to try fixing each issue.

Reasons for Error Code 11Solutions
Defective igniter coilReplace igniter coil
Defective igniterReplace igniter
Insufficient or restricted gas flowEnsure the gas service to your home is On. Next, check the gas valve at the bottom of the unit and ensure you turn it on.
Improper gas pressureTest and adjust gas pressure
Defective gas solenoid valvesReplace printed circuit board
Damaged igniter wire harnessInspect and replace damaged wires
Ventilation issuesInspect and clear exhaust vents
Dirty flame rodClean flame rod sensor

01. Defective Igniter Coil

A defective igniter coil is the number 1 culprit that causes your water heater to pop up the error code 11. 

If you have been 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: 

1. Start with unplugging the power cord. Then, turn off the gas valve, inlet water, and switch off the circuit breaker as well. 

2. Open the relief valve to let your heater drain the water.

3. 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. 

Igniter Coil On Rheem Tankless Water Heater
*Rheem Tankless Water Heater Igniter Coil Location*

4. Then, grab your new igniter coil (the part number of it is RTG20235C) and install it in the place of your old igniter coil. 

5. Finally, screw up the igniter coil and put the plastic insert back into its place to complete the installation.

02. Defective Igniter

An igniter is the component that is involved in the ignition process. It signals the unit to start heating water. Based on signals, its control board initiates the ignition sequence.

If the igniter goes bad, the control board receives no signals to start the ignition sequence. In short, the tankless water heater won’t ignite due to a defective igniter. 

And when the tankless water heater fails to ignite the burner, it will throw the error code 11 on the controller display. 

How To Fix: 

Replace the igniter to resolve this issue. Let’s learn the procedure of Rheem Tankless Water Heater Igniter Replacement

  • Unscrew the front panel by removing screws using a Phillips head screwdriver.
  • Locate the igniter on your tankless unit and remove the plastic insert to unplug the igniter coil. 
  • Unscrew the nut that holds the igniter in place and gently remove the igniter. 
  • Now, install a new igniter and secure it with the bolt. Attach the igniter coil to the igniter by inserting the plug.
  • Replace the front panel and turn on the unit.

03. Insufficient Or Restricted Gas Flow

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. 

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 coming is another way to inspect the gas flow.

04. Improper Gas Pressure

Improper gas pressure is the third culprit I blame if there is an ignition issue or the unit throws the error code 11. 

How To Fix: 

You can’t tell whether the gas pressure is low or right unless you test it.

The recommended inlet gas pressure for a tankless water heater powered by natural gas is 4″ WC-10.5″ WC. On the other hand, the gas pressure should be between 8″ WC and 14″ WC if you have tankless water heater fueled with propane.

I recommend you hire a professional if you don’t have the tools and the knowledge to work with gas appliances. On the other hand, you can check the following tutorial to check the gas pressure if you are fairly handy

05. 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 the 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. 

06. 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. 

07. Ventilation Issues

Proper ventilation is the first priority for a gas tankless water heater for safe operation. If the tankless unit doesn’t receive sufficient oxygen for combustion, it can lead to ignition issues.

How To Fix: 

Inspect the ventilation system and ensure there is no blockage. Clear the exhaust vents if needed to gain proper air circulation. 

8. Dirty Flame Rod

The flame rod senses the flame and sends the signals to the control board. If the flame sensor gets dirty, it won’t sense the flame and interrupt the ignition process. 

How To Fix: 

Cleaning the flame rod sensor will help you resolve this issue. Fortunately, I published an article on Rheem Tankless Water Heater Flame Rod Cleaning. Read this article and learn how to clean the flame sensor following seven simple steps.

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 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 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?

In some cases, resetting your water heater will bring a bit of luck to you and reset the error code 11. To reset the unit, follow these steps:

  • Turn off the gas supply to the unit and unplug it from the electric outlet.
  • Leave the unit for 30 seconds.
  • Plug the unit again and turn on the gas supply. 

I hope it will reset the tankless water heater. 

What Maintenance Steps You Should Take to Prevent Error Code 11?

Preventive maintenance will help you avoid error code 11 and ensure the optimum efficiency of your tankless water heater. Regular maintenance workflows include: 

  • Flush your tankless water heater once a year. If you live in an area where the supply of water contains significant minerals, flush the unit every six months. 
  • Inspect the air intakes and exhaust vents periodically and clean them. If required, replace those parts. 
  • Check the flame sensor rod and ensure it doesn’t get covered with buildup. If cleaning the sensor rod won’t bring any luck, replace the flame sensor rod. 
  • Ensure your tankless water heater gets sufficient gas supply and verify the gas pressure is within specifications. 
  • Clean or replace the igniter. 

If you want to explore the complete maintenance checklists and procedures, read this article on Rheem Tankless Water Heater Maintenance.


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. 

Read Also:

Similar Posts


  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. My Rheem combi boiler goes into error 11 from time to time but when I turn power off and back on it works fine again. What could that be?

  3. I got error c11
    I checked voltage across PGRF AND MAIN GAS both doesn’t shows voltage across it both valve resistance is fine
    I can heard igniter chattering and also fan is on SV 1. 2 and 3 shows voltage across it
    Any one can help me on this ?

    1. Look for other culprits I mentioned in this guide. If you still fail to resolve the issue, don’t forget to flush your tankless water heater. I hope it will help you erase the error code. If the problem still persists, call a professional for further assistance.

  4. Hey Eric, Garry here.
    Just replaced ignition coil and burner assembly. STILL throwing a code 11! Can see ignition start in little view window, but goes out shortly thereafter. Any help would be appreciated

    1. What’s the last time you flush your tankless water heater? Flush the water heater. Also, don’t forget to look for other culprits as well to erase the error code 11. If the problem still persists, call a professional for further assistance.

Leave a Reply

Your email address will not be published. Required fields are marked *