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
The same code number can mean something different on another series — make sure you're reading the page for your exact unit:
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: