Rinnai Water Heater Code 25
The Short Answer: Rinnai 25 is a condensate problem on condensing units — trap full, hose kinked or frozen, or a field-installed condensate pump that died. It is not an igniter code. Unkink the drain. Empty the pump reservoir. One reset. Water on the PCB or a 25 that returns is licensed. Non-condensing R53/V units should not be throwing 25.
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Search Intent & The Real Problem
High-efficiency Rinnai (RU, RUR, SENSEI, many indoor condensing) make acidic condensate on purpose. That water has to leave. When it cannot, the board posts 25 (condensate pump / drain) or, on some SENSEI firmware, a 10 with a full trap. The shower dies. People replace flame rods. Related wet paths: Navien condensate, tankless drains excessively, Rinnai leaking from the bottom.
What other guides get wrong
They call 25 a “combustion fault” and send you into the burner. They tell you to pinch the condensate hose so it “stops leaking.” A pinched hose is how you get 25, then 10, then a wet board. They treat every drip as a heat-exchanger failure. Cool water from the PVC drain while the burner runs is condensate, not a tank leak.
Step-by-Step Troubleshooting
Step 1: Confirm 25 on a condensing Rinnai
| Code | Meaning | First look |
|---|---|---|
| 25 | Condensate pump fault or blocked drain | This page |
| 10 | Air / exhaust, or full trap on SENSEI | Code 10 |
| 12 | Flame failure | Code 12 |
| 16 | Outlet over-temp | Scale / low flow |
| 79 (some firmware) | Water leak detected | Shut down |
- What to look for: PVC or vinyl drain at the bottom, PVC vent (condensing). A stainless Category III V/R53 with a “25” is a misread or the wrong brand’s chart.
- Required tools: Phone photo of the code and the rating plate.
Step 2: External drain — kink, freeze, uphill, glue blob
- What to look for: Hose crushed by the unit, run uphill to a sink, stuffed into a standpipe with no air gap, frozen at an outdoor termination. Neutralizer jug packed so nothing leaves. Cool drip at a loose union that looks like a bottom leak.
- Required tools: Eyes, wet/dry vac on the external line only.
Unkink. Thaw a frozen outdoor hose with warm air, not a torch. Glue in the trap from the original install is a licensed cut-out.
Step 3: Condensate pump (if you have one)
- What to look for: Field pump under the unit with a reservoir full, float stuck, or discharge line frozen on the way to a laundry sink. Rinnai 25 specifically calls out a pump accessory on many manuals: wiring off, reservoir not empty, pump dead. Pump that runs dry and screams is a different noise.
- Required tools: Dump the reservoir into a bucket. Power off first if you are unplugging the pump.
A pump that fills again in minutes with no hot-water use is a potable leak, not condensate. Shut the isolation valves.
Step 4: Inside the cabinet — stop if the board is wet
- What to look for: Water behind the front cover, mineral tracks on the PCB, trap overflowing inside. That is no longer a hose. Power stays off. Acid on electronics is a board replacement after the drain is fixed — not a hair dryer on a live PCB.
- Required tools: Flashlight. Do not pull the trap apart if you cannot reseal it.
Condensate in the secondary exchanger also starves the fan — you may see 10 after 25.
Step 5: One reset after the drain flows
- What to look for: Drain free, pump empty and pumping, no water on the board. Power off 10–30 seconds. 25 gone, unit fires, condensate beads at the drain while it runs — that last part is normal. Same 25 on the next shower: licensed. Do not keep resetting a flooded cabinet.
- Required tools: Hand on the switch.
When DIY Ends: Calling a Licensed Pro
Stop at a wet PCB, a stream from inside the jacket, a frozen line in a wall, gas smell, or a 25 that returns. You may unkink the hose, empty a pump reservoir, and power-cycle once. Internal trap service, exchanger work, and board replacement are licensed. Rinnai will not cover an exchanger that ran with a blocked condensate line.
Frequently Asked Questions
Q: What does Rinnai code 25 mean? A: Condensate is not leaving — blocked drain, full trap, or a failed condensate pump. It is not an igniter or gas-valve code.
Q: Can I clear a Rinnai 25 myself? A: If the hose is kinked, frozen at the end, or the accessory pump reservoir is full, yes. If the cabinet or board is wet, or 25 returns, hire a licensed tech.
Q: Is condensate dripping from a Rinnai a leak? A: Cool drip from the drain fitting while it fires is normal condensate. Hot water from inside the jacket, or the T&P, is not — shut it down.