Rinnai Rinnai RL75iN RL Series Tankless Water Heater 29 Error Fix: Condensate Drain Sensor Fault

Error code 29 on the Rinnai Rinnai RL75iN RL Series Tankless Water Heater means: Condensate Drain Sensor Fault. The condensate drain sensor or float switch has failed or is reading an abnormal condition. This code applies to condensing models only. The condensate sensor monitors the condensate trap and drain to ensure proper drainage. Error 29 indicates the sensor itself has malfunctioned rather than an actual drainage blockage (compare with error 25). The sensor float may be stuck in the up position (indicating full when it is not), the sensor contacts may be corroded, or the wiring to the sensor may be damaged. Inspect the condensate trap and sensor assembly. Clean the float mechanism. Check the wiring connections at the sensor and control board. Replace the sensor if cleaning does not resolve the issue. On some models, the condensate trap assembly includes the sensor and is replaced as a complete unit.

The most successful fix is "Replace the Condensate Drain Sensor Assembly" (medium difficulty, ~30 minutes). Estimated DIY cost: $20-$30. HomeMD has 2 community-ranked fixes for this error.

This error is rated warning severity. It is generally not urgent and can often be resolved with a simple DIY fix.

Yes — the top-ranked community fix ("Replace the Condensate Drain Sensor Assembly") is rated medium difficulty and takes about 30 minutes. Tools needed: Phillips screwdriver, Multimeter.

DIY cost: $20-$30. Professional repair typically costs $150-$220. Many homeowners save money by trying the top-ranked community fix first.

The Rinnai Rinnai RL75iN RL Series Tankless Water Heater has 8 other known error codes, including: 02 (Ignition Failure), 03 (Bath Fill Function Abnormality), 05 (Blocked Exhaust / Air Supply), 10 (Blocked Exhaust — Air Pressure Switch), 11 (No Ignition), and 3 more.

Error code 29 also appears on 8 other Rinnai models: Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater, Rinnai RL94iN RL Series Tankless Water Heater, Rinnai RSC160iN Condensing Combi Boiler, Rinnai RU130iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RU199iN Sensei Super High Efficiency Plus Tankless Water Heater, Rinnai RUR199iN Sensei Recirculating Tankless Water Heater, and 2 more. The fix may vary by model, so check each model's specific page for tailored repair steps.