How to fix Rheem tankless water heater code 11 [Easy steps]

Learn how to easily fix Rheem tankless water heater code 11 with these simple steps. Discover why this error occurs and how you can troubleshoot the issue yourself.

Rheem tankless water heaters are known for their efficiency and reliability, but encountering error code 11 can be frustrating. This code 11 indicates an ignition failure,( you can notice that no flame in the burning chamber through the burner sight glass) and there are several reasons why it may occur. In this comprehensive guide, we will explore the possible causes of Code 11 and provide step-by-step solutions to help you resolve the issue and restore your hot water supply.

rheem water heater error code 11 from user manual

How To Fix Rheem Tankless Water Heater Code 11: The Reasons & Solutions

1. Insufficient or Restricted Gas Flow

The first thing to check when you encounter Code 11 on your Rheem water heater is the gas supply. Ensure that your propane or gas tank has enough fuel to operate the water heater. Lift the tank to gauge its weight; if it feels light, it may be empty.

gas valve open condition and close condition

Next, verify that the gas is flowing to the burner by checking the gas valve. Ensure the red gas valve is aligned parallel with the pipe to allow gas flow. If you suspect the gas valve is damaged or worn out, consider replacing it.

Related: Rheem water heater pilot light won’t stay lit [easy fix]

2. Ensure proper sized regulator is used

Ensure the two stage regulator used on the inlet gas supply is at least six feet from the inlet gas supply to the water heater. Make sure when water heater shuts off, the pressure from the two stage regulator does not exceed the maximum inlet pressure of the water heater and that you have no bleed-though. To verify this, connect a
manometer up to the test port on the bottom of the water heater. The inlet gas pressure should never exceed 10
inches water column for natural gas or 13.5 inches for propane. If it does, the regulator may be defective.

3. Damaged Igniter Wire Harness

rheem tankless water heater ignitor coil replacement and its location

So, sometimes when your Rheem tankless water heater shows error code 11, it could be because of a damaged igniter wire. Don’t worry, it’s actually quite common. The wiring of the igniter can get cracked or damaged due to wear and tear. If the wiring gets damaged, the ignitor wont work.

To fix this issue, you’ll need to visually inspect the igniter wiring. Just remove the burner cover and take a look at the wire harness. If you notice any signs of wear or damage, it’s time to repair the wiring. Now, if you’re not really into electronics, no problem! Just give a professional electrician a call and they can replace the wiring for you.

4. Defective Igniter Coil

rheem tankless water heater ignitor and burner sight glass location

If the previous troubleshooting steps didn’t resolve the issue, it’s possible that you have a faulty ignitor coil. The ignitor is a small component responsible for sparking and igniting the flame that heats the water.

To check if the ignitor is functioning correctly, first, turn on the heater and look through the burner sight glass to look for flame or sparks. If the fan is operational but the ignitor doesn’t spark, you can perform a voltage test on the ignitor during ignition. To do this, cycle your water heater to initiate the ignition process and then measure the voltage across the connector wires of the ignitor. The normal voltage range should be between 11 to 13 VDC. If there is not voltage coming from the power control board to the ignitor, we need to replace the whole PCB.

If the voltage is in the above range, takeout the ignitor and visually inspect for carbon buildups, or dirt, if possible try to clean it with low grit sand paper, if it looks damaged you need to replace the ignitor coil which is nearly between 25-30$ by following the below steps.

How to replace the ignitor

When dealing with your Rheem tankless water heater’s igniter coil replacement, it’s essential to follow a few simple steps. First, ensure your safety by unplugging the power cord and turning off the gas valve and inlet water.

To begin the process, you’ll need to drain the water from the heater. This can be done by opening the relief valve, allowing the water to drain out.

Links to buy:

Next, locate the igniter coil, which can be identified by its part number, RTG20235C. Remove the screw that holds it in place and carefully follow the igniter wiring to pull out the plastic insert. This will allow you to remove the old igniter coil from its position.

Now, it’s time to introduce the  new igniter coil, which should also be part number RTG20235C. Carefully install it in place of the old one, ensuring it fits snugly.

To complete the installation, secure the new igniter coil by screwing it into position. Don’t forget to put the plastic insert back where it belongs, securing it properly.

5. Verify the Ventilation

Inspect the venting system for any obstructions that may hinder airflow. Clear away debris or nests that could block the ventilation which effect the combustion process.

By following these steps, you can troubleshoot and resolve Code 11 on your Rheem tankless water heater. Remember to prioritize safety and seek professional assistance if needed. With proper maintenance and care, your Rheem tankless water heater will continue to provide you with reliable hot water for years to come.

6. Defective Gas Solenoid Valves

When encountering the error code 11 on your tankless water heater, one of the potential culprits could be faulty gas solenoid valves. These essential valves play a crucial role in regulating the flow of gas to the main burner for ignition. If the main burner fails to ignite despite the igniter and fan functioning correctly, it indicates an issue with one of the gas solenoid valves.

Measure resistance or voltage of the Gas Valve Solenoid on PC Board at Connector D: Connector “D” on PC Board black wire pin #27 and yellow wire pin #29 = 18 ~ 22 ohms or 11 ~ 13 VDC respectively.


Code 11 on your Rheem tankless water heater indicates ignition failure. Follow our troubleshooting steps to identify the cause and resolve the issue. If you have further questions or need assistance, feel free to leave a comment below. We are here to help you get your hot water supply back up and running.

Link to user manual : here

TanklessHelp Staff

TanklessHelp Staff has an experienced writers and researchers in the field of water heating technology. With a background in HVAC and plumbing, Tanklesshelp staff has in-depth knowledge in many types of waterheaters in America and Canada. They have a passion for educating homeowners and businesses on solving easy to hard repairs and guide them on how to maintain them to save money.

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