How to Troubleshoot Rinnai Error Code 10 – Repair Tips

Rinnai tankless water heaterRinnai

Rinnai error code 10 indicates that the air supply or exhaust system is blocked or has some restrictions to disrupt normal airflow or flue gas extraction. The air pressure sensor measures the airflow.

This applies to all tankless water heaters from this manufacturer. 

Models coming from the Sensei series, which includes RUR and RU models, would also display an error code 10 if the condensate trap is full.

Troubleshooting Rinnai error code 10 – Causes

There are several reasons why the code 10 occurs:

  • Venting system is obstructed
  • Venting is not installed correctly 
  • Venting type, lengths, material, and clearances are not per specs
  • Contaminants present inside the venting system
  • Defective sensor
  • Dip switch is not in the right position
  • Fan blower has a blockage or is malfunctioning
  • Check valve is stuck
  • Condensate build-up and clogged line
  • Gas pressure is incorrect
  • High altitude setting is inaccurately set
  • Problems with the PC board

Tip: Before trying to repair or change any of the affected parts, try first to "restart" the unit by turning it ON and OFF. It could solve the problem. If it doesn't work, follow the troubleshooting steps below, or contact a professional plumber/technician.

Venting problems

Always buy Rinnai original components and what is recommended for your Rinnai model. Yes, there are many aftermarket parts available, but only the original components should be used.

Rinnai-approved venting material and accessories can be found here.

The code 10 would show up if the wrong venting material is used, venting elements are not correctly connected, if it is incorrectly sized, or something is blocking normal air intake or exhaust.

How to check if the venting system is causing a diagnostic code 10?

Remove the exhaust pipe located at the top of the water heater and turn your Rinnai water heater ON. If the water heater is still coding out, then the problem is not with the venting system.

Disassemble all the connections, confirm there are no damages on the pipes (such as significant dents and changes in its diameter), remove all the dirt and debris, and re-assembly it again, following the manufacturer's instructions. As mentioned before, verify the right venting type is used, the number of elbows is not exceeded so as the maximum length, and recommendations for the proper clearances are followed.

Removing the vents is only temporarily – for testing. It must always be installed while working to direct the flue gases outdoors – safely and have an uninterrupted air intake.

For the normal operation of the vent system, inspect it at least once a year.

Condensate is not draining

If the condensate trap is full and doesn't drain, the condensate line becomes clogged, causing you only problems. Blockage in the condensate line will trigger a diagnostic code 10, which will appear on the control panel display or a remote controller. The condensate line can become clogged due to the presence of dirt, or if it freezes up, or the line gets damaged. Check the condensate collar if it is properly installed and is not loose.

emergency plumber

Malfunctioning fan blower

To check the electric blower for proper work:

  • Turn OFF the power to a water heater.
  • Inspect the fan housing, wheel, motor, wiring harness, and anything that might prevent the fan from working correctly.
  • Clean the fan assembly from contaminants.

Dirty air filter

This applies to indoor models only. Make sure that the internal air filter is clear of debris, lint, and dirt. You can use dish soap and a soft brush to clean it. Try to inspect the air filter periodically and as specified by Rinnai. Once you remove the front panel, it is easy to locate the air filter at the unit's upper/right-hand corner.

Dirty burner assembly

Follow the instruction provided by the Rinnai manufacturer to remove the heat exchanger and gas burner assembly. Clean out the elements (heat exchanger, copper fins, gas burner, an orifice) from debris, dirt, carbon deposits, mineral build-up, and insects. There must be no blockage of any type so that nothing can cause airflow restrictions.

DIP switch positioned improperly

Ensure that high-altitude parameter settings (DIP switch) are correctly chosen for your place, where your Rinnai tankless is installed. You can adjust the PC board parameters using one of four selections, where the maximum altitude is 10,200 ft.

Where it applies, a DIP switch should be in the right position for the chosen vent length.

Incorrect gas pressure

Low and high fire pressures on the gas manifold should be set as specified by the manufacturer. If this is not adjusted accurately, the sensor won't be able to recognize the temperature change.

Important: Always hire a licensed professional to service or fix your Rinnai tankless water heater.

If you are planning to do it yourself, always turn OFF gas, water, and electrical supply.

How to display diagnostic codes

  • Turn OFF a tankless water heater.
  • Press and hold the ON/OFF button for a few seconds and then press the UP button simultaneously.
  • The last nine codes show up on display.
  • To return to the previous menu, press and hold the ON/OFF button for a few seconds and press the UP button at the same time.
  • Turn the power ON by pressing the ON/OFF button again.


Rinnai tankless water heaters can show error code 10 for various reasons. As you can see from the above text, troubleshooting diagnostic code 10 in some instances is not complicated and doesn't require you to call a plumber.

You can do it by yourself. In other situations where the repair requires advanced knowledge, experience, and special tools, you might want to contact a licensed technician.

Dealing with an innovative device and cutting-edge technology, as found in Rinnai, could lead to even more problems, void the warranty, or put you and your family in danger.

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