Welcome! Here are the website rules, as well as some tips for using this forum.
Our Rinnai RL75i water heater has been giving us a code 10 after 8 years of flawless operation. I have flushed the heat exchanger, cleaned the fan and cleaned the burner with the help of an excellent Rinnai service tech. The exhaust and air intake are clean and unobstructed. The tech thoroughly checked the unit and said everything looked ok. We are still getting the code 10, usually from running bath water in the upstairs bathroom. If we turn off the water and turn it back on everything is fine although occasionally we have to do this a second time and rarely a third time. The tech said if the code 10 continues the next step would be a more complicated check of the electronics. Can anyone give me any ideas on what to do next?