Rinnai Non-SENSEI Code 65
Water flow control valve fault. The water flow servo — the valve that meters how much water goes through the heat exchanger — did not close when the bath fill function asked it to. Rinnai's instruction if that happens is immediate: turn off the water flow and stop using the bath fill controller. After a power cycle to see whether the code clears, the answer is replacing the servo.
Part replacementThe verdict
Replace a part
Try a power cycle, because Rinnai does. If the code stays, it is a servo replacement — a moderate part with the unit opened and the supplies off. Stop using bath fill in the meantime.
Typical cost: $200–$600
US estimate for parts and labor. Prices vary by region and by who does the work — see how we estimate costs.
What the manual says
The meaning above is transcribed from the manufacturer's diagnostic documentation for the Non-SENSEI — not averaged across the brand.
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 55), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Stop using the bath fill function until this is fixed — a valve that will not close is what the code is reporting.
- Switch the unit off at the wall or breaker, wait a minute, and switch it back on to see whether the code clears.
- If it returns, book a service call for the water flow servo.
Code 65 on other Rinnai series
Other Rinnai series report code 65 under the same fault name, but each manual is transcribed separately and they do not read alike:
Don't confuse this with
2 other Rinnai Non-SENSEI codes point at a valve too. They are different components in different places, and ordering a part against the wrong one is the most common way this fault gets expensive: