Rinnai Rinnai V75iN Value Series Tankless Water Heater 03 Error Fix: Bath Fill Function Abnormality

Error code 03 on the Rinnai Rinnai V75iN Value Series Tankless Water Heater means: Bath Fill Function Abnormality. The bath fill auto-shutoff function has detected an abnormal condition. This code is primarily found on Rinnai models equipped with the optional bath fill feature, which automatically stops water flow once the tub reaches a preset level. Error 03 indicates the bath fill sensor detected an issue such as a failed flow sensor, a stuck bath fill valve, or an incorrect setting. This feature is more common on Rinnai models sold in Japan and Australia than in the US market. On US models that support this function, check the bath fill adapter connections and flow sensor. Power-cycle the unit to reset. If the bath fill feature is not in use, this code should not normally appear — if it does, there may be a control board issue reading a phantom signal.

The most successful fix is "Replace Bath Fill Flow Sensor or Repair Valve" (medium difficulty, ~45 minutes). Estimated DIY cost: $15-$30. HomeMD has 2 community-ranked fixes for this error.

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

Yes — the top-ranked community fix ("Replace Bath Fill Flow Sensor or Repair Valve") is rated medium difficulty and takes about 45 minutes. Tools needed: T20 Torx screwdriver, Multimeter, Adjustable wrench.

DIY cost: $15-$30. Professional repair typically costs $200-$300. Many homeowners save money by trying the top-ranked community fix first.

The Rinnai Rinnai V75iN Value Series Tankless Water Heater has 8 other known error codes, including: 02 (Ignition Failure), 05 (Blocked Exhaust / Air Supply), 10 (Blocked Exhaust — Air Pressure Switch), 11 (No Ignition), 12 (Flame Failure), and 3 more.

Error code 03 also appears on 8 other Rinnai models: Rinnai RE180iN RE Series Non-Condensing Tankless Water Heater, Rinnai RL75iN RL Series 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, and 2 more. The fix may vary by model, so check each model's specific page for tailored repair steps.