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Rinnai code 25: Sensor fault or condensate blockage

Continuous flow hot water system (Australia), tankless water heater (United States)

This code means one of two things, depending on your model. Find your model family below, then read the section for it. The model number is on the rating label on the side of the unit.

Find your model family

If you haveIt means
HD32e, HD28i, HD28e, Infinity, Infinity B, Infinity Enviro 26, Infinity Enviro 16, Infinity internal Neutraliser tank sensor fault
Commercial (KB), KB, KBD, KBP, KCM, Luxury (VC), SENSEI commercial, SENSEI residential, SENSEI residential with pump, Value (VC) Condensate pump error or drain clogged

Neutraliser tank sensor fault

On HD32e, HD28i, HD28e, Infinity, Infinity B, Infinity Enviro 26, Infinity Enviro 16, Infinity internal.

On condensing models with a condensate neutraliser, the neutraliser tank sensor has reported a fault.

This needs a licensed gasfitter. There is nothing safe to check yourself. Leave the covers on and book a professional.

What causes it

  1. The neutraliser tank electrode needs checking or replacing.

    Book a licensed gasfitter

How to read this code on your unit

Booking a licensed gasfitter

Book a licensed gasfitterlicensed gasfitter

  1. Turn the unit off and leave the covers on. Gas components must only be serviced by a licensed technician.
  2. Note the code, how often it appears, and the model and serial numbers from the rating label.
  3. Book a licensed gasfitter and give them those details.

Models that show this code

19 models in 5 ranges
RangeModels
Heavy Duty (commercial)REU-AM3237WC (HD32e), REU-VCM2837FFC (HD28i), REU-VCM2837WC (HD28e)
InfinityREU-AM3237W (Infinity 32), REU-AM2626WDL (Infinity 26 Touch), REU-AM2626WD (Infinity 26), REU-AM2024WD (Infinity 20), REU-AM1620WD (Infinity 16), REU-AM1220WD (Infinity 12), REU-A2626WB (B26), REU-A2024WB (B20), REU-A1620WB (B16)
Infinity BREU-BM2626W (Infinity B26), REU-BM2024W (Infinity B20), REU-BM1620W (Infinity B16), REU-BM1220W (Infinity B12)
Infinity EnviroREU-E2626W (Infinity Enviro 26), REU-E1620W (Infinity Enviro 16)
Infinity internalREU-VCM2837FF (Infinity 28i)

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

Condensate pump error or drain clogged

On Commercial (KB), KB, KBD, KBP, KCM, Luxury (VC), SENSEI commercial, SENSEI residential, SENSEI residential with pump, Value (VC).

Condensate has backed up and tripped the float safety switch, or the accessory condensate pump has stopped working.

You can often clear this yourself. Work through the causes below in order, most likely first.

Water may be leaking. Turn off the water supply to the unit if you see a leak.

What causes it

  1. The condensate pump has no power or has stopped working.

    Check the condensate drain is not blocked or frozenYou can do this

    1. Follow the small plastic condensate pipe from the unit to where it drains.
    2. Check it is not kinked, crushed, blocked at the outlet, or frozen in cold weather.
    3. If it uses a condensate pump, check the pump is plugged in and powered.
    4. If the pipe is frozen or blocked inside the unit, leave it and book a technician.

    Book a licensed plumber

  2. The drain line is clogged or frozen, or has no air gap.

    Same check as above: Check the condensate drain is not blocked or frozen

    Book a licensed plumber

How to read this code on your unit

Booking a plumber

Book a licensed plumberplumber

  1. Note the code, the model and serial numbers, and what the system was doing when the code appeared.
  2. Book a licensed plumber and give them those details.

Models that show this code

48 models in 10 ranges
RangeModels
Commercial (KB)C199i (REU-KBD3237FFUDC-US), C199e (REU-KB3237WDC-US)
KBRU80i (REU-KB2530FFUD-US), RU80e (REU-KB2530WD-US), RU90e (REU-KBD2934WD-US), RU98i (REU-KB3237FFUD-US), RU98e (REU-KB3237WD-US)
KBDRUC80i (REU-KBD2530FFUD-US), RUC90i (REU-KBD2934FFUD-US), RUC98i (REU-KBD3237FFUD-US)
KBPRUR98i (REU-KBP3237FFUD-US), RUR98e (REU-KBP3237WD-US)
KCMRUCS65i (REU-KCM2025FFU-US), RUCS75i (REU-KCM2528FFU-US), RUS65e (REU-KCM2025W-US), RUS75e (REU-KCM2528W-US)
Luxury (VC)RL75i (REU-VC2528FFUD-US), RL75i(A) (REU-VC2528FFUD-US(A)), RL75e (REU-VC2528WD-US), RL75e(A) (REU-VC2528WD-US(A)), RL94i (REU-VC2837FFUD-US), RLX94i (REU-VC2737FFUD-US), RL94e (REU-VC2837WD-US)
SENSEI commercialCU199i (REU-N3237FFC-US), CU160i (REU-N2530FFC-US), CU199e (REU-N3237WC-US), CU160e (REU-N2530WC-US)
SENSEI residentialRU199i (REU-N3237FF-US), RU180i (REU-N2934FF-US), RU160i (REU-N2530FF-US), RU130i (REU-N2024FF-US), RU199e (REU-N3237W-US), RU180e (REU-N2934W-US), RU160e (REU-N2530W-US), RU130e (REU-N2024W-US)
SENSEI residential with pumpRUR199i (REU-NP3237FF-US), RUR160i (REU-NP2530FF-US), RUR199e (REU-NP3237W-US), RUR160e (REU-NP2530W-US)
Value (VC)V53e (REU-VAM1620W-US), V53De (REU-AM1620WD-US), V65i (REU-VC2025FFU-US), V65e (REU-VC2025W-US), V75i (REU-VC2528FFU-US), V75e (REU-VC2528W-US), V94i (REU-VC2837FFU-US), V94Xi (REU-VC2737FFU-US), V94e (REU-VC2837W-US)

Where this comes from

Checked against the manufacturer's manual on 9 October 2026.

Other Rinnai tankless water heater codes

Code Meaning What you can do
17 Venturi blockage Safe checks first, then a pro
18 Gas valve adjustment limit Call a pro
19 Electrical earth fault Call a pro
21 Data transfer or dip switch error Call a pro
22 Gas valve adjustment fault Call a pro
32 Outgoing water temperature sensor fault Call a pro
33 Heat exchanger thermistor fault Call a pro
34 Temperature sensor fault (depends on model) Call a pro
36 Lower tank thermistor fault Call a pro
38 Exhaust temperature thermistor fault Call a pro
72 Flame rod circuit error Call a pro
73 Burner thermocouple fault Call a pro

See all sensor fault codes on tankless water heaters across brands.

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