Rinnai Tankless Water Heater Code 11

Rinnai Tankless Water Heater Code 11 [How To Fix]

This is a complete troubleshooting guide on Rinnai Tankless Water Heater Code 11. Let’s check the 7 reasons at a glance that cause the unit to pop up the fault code 11: 

  • Gas supply to the unit may turn off
  • Incorrect gas type or wrong inlet gas pressure
  • Air in the gas lines
  • Wires leading to PC board gets damaged 
  • Loose flame rod wire
  • Loose or floating flame rod
  • Dirty to defective igniter

The best part is- I will walk you through every troubleshooting step to fix those 7 culprits to clear the error message. 

So, let’s get started. 

Table of Contents

What Does Error Code 11 Mean On Rinnai Tankless Water Heater?

Error code 11 indicates a problem with the ignition system (no ignition). Your Rinnai Tankless water heater will throw this fault code due to insufficient gas or incorrect inlet gas pressure, defective igniter, and dirty flame rod. 

Besides, air in the gas line, loose or damaged flame rod wire, incorrect gas orifice, and blocked condensate line are some culprits that can cause the error code 11. 

To erase the error message, you must troubleshoot all the issues I mentioned and fix them. The next chapter will walk you through every troubleshooting step to solve this water heater issue. 

Rinnai Tankless Water Heater Code 11 [7 Easy Solutions]

This chapter will introduce you to the all possible culprits responsible for the error code 11. Nonetheless, I will walk you every troubleshooting step to fix those issues.

01. Gas Supply May Turn Off

You can’t ignite your gas tankless water heater without fuel. If you don’t turn on gas at the unit, meter, or cylinder, your water heater won’t get any fuel for combustion. And when you try to ignite the unit without turning on the gas supply, the unit will throw the error code 11. 

How To Fix: 

First off, check the gas control valve at the unit. Ensure you turn it counterclockwise to let the gas supply to the unit. On the other hand, if you have a propane tank, make sure the valve on the tank is at the on position. 

02. Incorrect Gas Type or Wrong Inlet Gas Pressure

Rinnai Tankless Water Heater is operated either with natural gas or propane gas. If you use the wrong type of gas, you will never ignite the unit. Similarly, the inlet gas pressure should be within limits. Otherwise, it will cause error code 11. 

How To Fix: 

Check the manual and ensure you use the right type of fuel. If the unit requires natural gas for operation, power up the water heater with gas. Otherwise, connect your water heater with the propane line. 

Next, ensure there is correct inlet gas pressure at the unit. On a Rinnai gas tankless water heater, the gas supply pressure should be between 3.5” WC to 10.5” WC. On the other hand, the inlet gas pressure on a propane unit should be between 8” WC to 13.5” WC. 

I highly suggest you call a qualified technician if the gas supply pressure goes out of range. 

03. Air In The Gas Lines

Before turning on your tankless water heater, you should purge all the gas lines. If there is dirt or air in the gas lines, your water heater will not work properly. Sometimes, air in the water lines can also affect the water flow and it prevents the unit from lighting. And guess what, it will cause the unit to pop up the error message 11. 

How To Fix: 

Generally, a tankless water heater will purge the line in seconds with the high gas flow. What I recommend you is- open the service valve and leave your water heater until you clearly smell the gas. Once you smell the gas, close the service valve and wait another few minutes before connecting the gas line to the water heater. 

Bleeding air from water lines is also a must if you want to operate the unit trouble-freely. Just turn on the hot water faucets slowly and run the faucets for several minutes to allow the air to pass through the water pipe. Keep the hot water faucets opened until no more air bubbles are coming out of the faucet. 

04. Wires Leading To PC Board Gets Damaged

If the wirings leading to the PC board come loose or get damaged, the unit can throw an error code 11. You can find five different electric connectors on your Rinnai tankless water heater. Check wires on each connector and look for visual damage. 

How To Fix:

It will be best if you call a certified electrician to inspect the wiring leading to the PC board. If needed, you may need to replace the wiring or the PC board itself. The following tutorial will come into play for PC board installation: 

05. Loose Flame Rod Wire

Ignition failure is a result of loose wiring to the flame rod. If the wires of the flame rod gets damaged or disconnected, you will fail to ignite your tankless water heater. Turns out, plugging the flame rod wire into the proper flame rod can cause the unit to pop up the code 11. 

How To Fix: 

Again, I recommend you call a professional to inspect the flame rod wiring of the unit. If needed, he will replace the flame rod wiring or the flame rod itself. 

06. Loose Flame Rod

A loose or floating flame rod on your Rinnai tankless water heater will cause an ignition issue. It should be tight in its mounting brackets. 

How To Fix: 

Firstly, remove the upper access panel of the unit. Then, locate the flame rod and verify it is tight in the mounting bracket. You will never move it with your fingers if the gasket is intact. If loose, pull out the flame rod and clean it if needed. Then, reinstall it with a new gasket. 

07. Dirty or Defective Igniter

An igniter is what helps to ignite the water heater. If this component gets dirty or defective, your water heater won’t ignite. As a result, it will showcase the error message 11 on the controller display. 

How To Fix: 

Turn off the unit and remove the access panel by unscrewing four nuts. Then, locate the igniter and clean it if there forms build up. If cleaning the igniter brings no luck for you, you must replace it. And this video will help you in this case: 


Rinnai Tankless Water Heater will display the error code 11 if the gas isn’t turned on at the unit, gas meter, or tank. Turns out, defective igniter, loose flame rod, and air in the gas line can cause the code 11 problem. 

Fortunately, I already broke down the reason behind this issue and what troubleshooting steps you should take. So, follow the guideline and clear the error message from the display.  

If the error code returns after trying out all the steps I mentioned, I bet there is something critical. So, turn off the unit and call a professional to handle this issue for you. 

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  1. Nice run through you have provided. Thanks.
    I might hope to hear from you about a wrinkle I am having with my Rinnai 2402 Continuum and getting code 11.
    The flame comes on great during initial start up three times bright and blue. So the igniters are doing their thing. But it does not go the next step and stay lit.
    I have tried all the things suggestions that I have come across and no where has this been mentioned except flame rod related troubleshooting. The continuity seems good and it is good and tight where it sticks in over the burners but I wonder if I am missing something. .
    A rainstorm did somehow infiltrate the right side via the intake vent and I found some water dripping along that side where the circuit board is bolted on. This has never happened! It wasn’t much but… I blew out the area as best I could and don’t know what to look for as far as damage there. Before I try to see if this is a part I can even get. I wonder if there is something else that might be a remedy. The two way vent is my next cleaning check. Figuring out how the water found it’s way in too.
    If one of these units is running I guess any water present around the vent would be drawn right in as a matter of course. Is the circuit board super sensitive to drops of water while running? Is it just toast now? What kind of testing can I try to rule this part out as the problem? Is that why the unit fires up and then shuts down with code 11 showing? Can this be addressd without replacing the board?

    1. Hey Andrew,

      Thanks for reaching us.

      The best suggestion I can offer you is to hire a certified electrician to have the circuit board tested electrically. You know the circuit board is super sensitive, especially to water. I think the water dripping causes an electric short circuit and fry up the circuit board.

      And without seeing the unit physically, it’s almost impossible to come to the conclusion.

  2. Do I need to shut off the unit if it throws a code of 11 till we can figure out what the problem on it is

    1. No, you don’t need to shut off the unit unless you are going to make an replacement like the igniter (it’s often responsible for the unit to throw the error code 11).

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