Rinnai tankless water heater code 25
Condensate pump fault or blocked condensate drain. Code 25 means the same thing on all 3 Rinnai series documented here — but the fix, and what it costs, is still worth reading for your exact unit.
What code 25 means on each Rinnai series
| Series | What it means | Verdict | Typical cost |
|---|---|---|---|
| Non-SENSEI | Condensate pump fault or blocked condensate drain | DIY fix | $0–$350 |
| SENSEI | Condensate pump fault or blocked condensate drain | DIY fix | $0–$350 |
| SENSEI RX | Condensate pump fault or blocked condensate drain | DIY fix | $0–$350 |
Each row opens the full page for that generation. We hold manuals for Non-SENSEI, SENSEI and SENSEI RX, and each one gets its own reading of code 25 — what Rinnai documents, what you can safely check yourself, and what the repair should cost.
What each manual actually says
The table above compares 3 series in four columns, which is enough to route you and not enough to explain anything. This is the Rinnai wording behind each row, one entry per manual, so you can see where the 3 readings of code 25 agree and where they part company.
Non-SENSEI — 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.
SENSEI — Condensate pump fault or blocked condensate drain
Condensate has backed up far enough to close the condensate safety switch, or an accessory condensate pump has stopped working. Rinnai notes the code appears when the float switch trips because condensate is not getting away — which on a condensing unit means a clogged, frozen, or badly routed drain line as often as a dead pump.
SENSEI RX — Condensate pump fault or blocked condensate drain
Condensate has backed up far enough to close the condensate safety switch, or the accessory condensate pump has stopped working. Rinnai notes the code appears when the float switch trips because condensate is not getting away — which on a condensing unit like the SENSEI RX means a clogged, frozen, or badly routed drain line as often as a dead pump.
Does it matter which Rinnai you have?
Non-SENSEI, SENSEI and SENSEI RX all route code 25 the same way: a replacement part, at $0–$350. That makes it one of the Rinnai numbers you can act on before working out which unit you own.
Which Rinnai do you have?
On the 3 series that report code 25, the model number on the rating label starts C, RC, RU, RUC and RUR — match yours against the 76 listed below. You can also use the full model-number decoder.
Where this comes from
Source: Rinnai Troubleshooting Tankless Water Heater Diagnostic Codes (100000652) (p. 34), read Aug 2026 — the manufacturer's own documentation for this Rinnai range.
Parts, guides and symptoms behind code 25
Code 25 on these 3 Rinnai series points at 1 part and 2 symptoms, each named by the manufacturer's own procedure for this code.