HVACopediaRinnai · Tankless water heater troubleshooting
Water leaking from pump housing
What is going on
Water weeping from the pump housing on a Rinnai tankless with a pump (SENSEI and Non-SENSEI). Water around the aluminum casing means the pump shaft O-ring has failed and is letting water toward the motor winding. Shut off power before inspecting, since water and electrical parts together are a shock hazard.
Likely causes
- Failed O-ring on the pump shaft
Check in this order
- Disconnect electrical power to the water heater, and shut off the water supply before working near the pump.
- Inspect the pump housing around the aluminum casing for water streaks or weeping.
- Look for corrosion or water marks on the nearby wiring and board.
- Replace the pump/motor assembly.
- After the repair, restore water and power and check for leaks during a run cycle.
- Have a licensed technician do the repair if you are not qualified.
Applies to: SENSEI and Non-SENSEI series with pump
More tankless water heater guides
- Checking PC board fuses and thermistors
- CO sensor / combustion air fault (code number not printed on these pages)
- CO sensor voltage check (PCB connector C1)
- Code 12 or 19 appears immediately after water flow starts (no flame in burner box)
- Cold water sandwich (temperature swings at fixture)
- Hot water still flowing with the unit off (bleed-down or cross-over)
Take it to the job
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Source: Troubleshooting Tankless Water Heater Diagnostic Codes, p. 60. Written in our own words; check the manual for your exact model.
For licensed technicians. Gas, electrical and refrigerant work must be done by a qualified, licensed person. Shut off power and gas before servicing, never bypass a safety control, and follow the manufacturer’s manual for the exact model; it and local codes always take priority. HVACopedia is not affiliated with any manufacturer; brand and model names only identify the equipment.