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Rinnai code 25 (condensate pump): what to check

By How House Works EditorialBased on Rinnai manualsChecked against sources Updated

Rinnai display

25

“Condensate Pump (Accessory)”

RU/RUR/RSC, RX · SENSEI RU Installation and Operation Manual, p. 74; SENSEI RUR Installation and Operation Manual, p. 73; SENSEI RSC Installation and Operation Manual, p. 73; SENSEI RX/CX Tech Sheet, p. 1; Troubleshooting Tankless Water Heater Diagnostic Codes, p. 34
Owner checks, then technician

What it means

Code 25 concerns an accessory condensate pump on a condensing RU, RUR, RSC or RX heater RU manual, p. 74. Rinnai calls for a condensate pump when there is no floor drain or the drain sits above the heater’s condensate drain RU manual, p. 54. When a pump is installed, its safety switch is wired to the heater so that the heater shuts off if the pump fails p. 55.

The troubleshooting guide says code 25 only appears when the condensate safety switch contacts are made, which happens when condensate backs up and trips the float switch, and that it may also occur if the pump stops working p. 34. The installation test in the RU manual sets the code on purpose: with the pump unplugged and its reservoir filled until the float switch closes, the heater shows 25 p. 55.

Check these first

  1. Check that the pump is plugged in. Rinnai says the field-supplied condensate pump should include an internal safety switch and a power cord, and that the power cord must be plugged into a power source SENSEI RX Installation and Operation Manual, p. 41.
  2. Check that the pump’s reservoir is empty and that the pump runs RU manual, p. 74.
  3. Check the condensate drain line: condensate flowing, the line not blocked, clogged or frozen, and its end open to the air RU manual, pp. 76–77.
  4. The code 25 row gives no reset step RU manual, p. 74. The RU manual’s installation test clears the code this way: turn off the heater with the On/Off button on the controller, wait five seconds, then turn the power back on p. 55.
  5. If 25 comes back, call for service.

When to call a licensed technician

  • The wire connections and harness between the pump and the heater RU manual, p. 74. The safety switch wires come from inside the heater cover, and the wiring must conform to local codes and the National Electrical Code RU manual, p. 55.
  • Drain line work. Rinnai specifies corrosion-resistant material such as PVC pipe or plastic hose, a diameter at least that of the 1/2 in. drain connection, a slope toward the floor drain or pump, and an approved supplemental heat source on lines in areas subject to freezing RU manual, p. 54.
  • The condensate trap inside the heater and an air gap in the drain line, both on the troubleshooting guide’s list p. 34.

Notes for different models

Code 25 appears only in the RU, RUR, RSC and RX/CX tables RU manual, p. 74; SENSEI RX/CX Tech Sheet, p. 1, although the troubleshooting guide applies it to Non-SENSEI models as well p. 34. The RE, REP, Value, V53De and VC tables have no code 25.

Related Rinnai codes

  • 10 “Air Supply or Exhaust Blockage/ Condensate Trap is Full”
  • 54 “High Exhaust Gas Temperature”

All Rinnai codes

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Sources

  1. Rinnai America Corporation. Troubleshooting Tankless Water Heater Diagnostic Codes. 100000652(03), 5/2024; for trained and qualified professionals. Accessed Oct 12, 2026.
  2. Rinnai America Corporation. SENSEI RU Installation and Operation Manual. 100000467(07), 1/2021; cover title: Tankless Water Heater (Residential) Installation and Operation Manual; listed on rinnai.us as N Series Residential Condensing Installation and Operation Manual. Accessed Oct 12, 2026.
  3. Rinnai America Corporation. SENSEI RUR Installation and Operation Manual. 100000508(07), 1/2021; cover title: Tankless Water Heater (With Pump) Installation and Operation Manual. Accessed Oct 12, 2026.
  4. Rinnai America Corporation. SENSEI RSC Installation and Operation Manual. 100000773(01), 1/2023. Accessed Oct 12, 2026.
  5. Rinnai America Corporation. SENSEI RX Installation and Operation Manual. 100000839(03), 3/2025 (from PDF metadata; not printed). Accessed Oct 12, 2026.
  6. Rinnai America Corporation. SENSEI RX/CX Tech Sheet. 100000849, U362-0875(00); no printed date or page numbers (p. 1 is the PDF page). Accessed Oct 12, 2026.