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