If you have a Rinnai tankless water heater, you probably love hot water whenever needed. But when you see Error Code 11 on your heater, it’s a big problem. It means your heater’s ignition isn’t working, and you won’t have hot water. Even more frustrating is that Error Code 11 can happen for different reasons. But don’t worry! This guide will explain, figure out, and fix the problem so you can have hot water again, step by step.

1. Ignitor Issues

The ignitor is often at the heart of Error Code 11 troubles. Here’s what to do:

Testing the Ignitor

  • Begin by cycling the unit and checking for sparks from the ignitor.
  • If you don’t see a spark, it could be due to loose or damaged components or incorrect voltage on the electric board.

Cleaning the Ignitor

  • Inspect the ignitor for scale or carbon buildup.
  • If you spot any, follow the manufacturer’s cleaning instructions to remove it.

2. Gas Supply Problems

A proper gas supply is essential for your tankless water heater. Here’s how to investigate gas-related issues:

Gas Supply Check

  • First, make sure you turn on your home’s gas supply.
  • Check other gas-powered appliances like your stove or dryer to ensure they receive gas.

Gas Pressure Issues

  • Incorrect gas pressure can result from dirt or debris clogging the gas system.
  • If you’ve recently installed your Rinnai water heater, Don’t forget you might have to remove any trapped air from the gas pipes.

3. Flame Rod Examination

The flame rod plays a vital role in ignition. Here’s how to inspect it:

Inspecting the Flame Rod

  • Sift through the flame rod and wiring to ensure everything is in good shape.
  • Check wiring connections to make sure they are secure and undamaged.

Cleaning and Replacing

  • Clean the flame rod or gasket thoroughly if you find dirt or debris.
  • If any parts are damaged or cracked, replace them promptly.

4. Venting Issues

Faulty venting can hinder your tankless water heater’s performance and trigger Error Code 11. Here’s how to tackle venting problems:

Clearing Blockages

  • Inspect the intake and exhaust vents for blockages and clear them as needed.

Venting Component Inspection

  • Thoroughly check the venting system, paying close attention to the installation and condition of components.
  • Incorrect installation or damaged components can disrupt airflow and contaminate flame rods.

5. Water and Moisture Concerns

Moisture-related issues can also contribute to Error Code 11. Here’s how to address them:

Leak and Moisture Inspection

  • Inspect the unit for any signs of leaks or excessive moisture, as these can lead to component corrosion and electrical issues.

Condensate Drainage for Condensing Units

  • If you have a condensing unit, inspect the condensate drainage system to ensure it functions correctly.


Encountering Error Code 11 on your Rinnai tankless water heater can be a frustrating experience, but as you’ve seen in this comprehensive guide, it’s a challenge you can tackle. With a better understanding of what might be causing the problem and clear, easy-to-follow solutions, you can feel sure about finding and fixing the issue.

Remember, if you ever are uncertain about any of these steps or if the problem persists, feel free to seek professional assistance. Your hot showers and endless supply of hot water are well worth it. 

So, get ready to restore the warmth and comfort of your home with a fully operational Rinnai tankless water heater. Say goodbye to Error Code 11 and hello to relaxing, hot showers once more.

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