Rinnai Non-SENSEI Code 25
Condensate pump fault or blocked condensate drain. The condensate safety switch closed, which happens when condensate backs up far enough to trip the float switch — or the accessory condensate pump has stopped working. Rinnai's checks are the pump's power supply, the pump itself, a drain line that is clogged or frozen, the wiring back to the PC board, an air gap in the drain line, and restrictions in the trap.
DIY fixThe verdict
Replace a part
Often free. A condensate line frozen where it leaves the building, or a pump that has lost power, is the usual answer and both are visible without opening the heater. A failed accessory pump is a modest part.
Typical cost: $0–$350
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. 34), read Aug 2026 — the manufacturer's own documentation for this exact series.
What you can safely check
- Follow the condensate line from the unit to where it drains. Look for a kink, a sag holding water, or ice where it passes somewhere cold.
- If there is a condensate pump, check it still has power — these are usually plugged into a nearby outlet that something else can trip.
- Empty and check the pump reservoir if it has one.
- If the line is clear and the pump runs, book a service call — the trap and the wiring back to the board are inside the unit.
Code 25 on other Rinnai series
Other Rinnai series report code 25 under the same fault name, but each manual is transcribed separately and they do not read alike: