E15
Rheem Booster Pump / Recirculation Pump Fault (models with built-in pump)

Rheem tankless water heater shows E15 and does not start

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Seized recirculation pump, Air-locked pump, Loose pump wiring, Faulty pump motor

How to Fix / Troubleshooting

Safety first: Turn OFF power and close water valves before removing any pump covers.

  • Listen for pump: When recirculation is called, you should hear the pump run. If it hums but does not move water, it may be air-locked or seized.
  • Bleed air: Open a hot water tap and briefly run the pump to purge air from the lines (follow Rheem's priming procedure).
  • Check valves: Ensure recirculation isolation valves are open and any check valves are correctly oriented.
  • Inspect wiring: Verify the pump connector is firmly attached to the control board and pump.
  • If pump is seized: Replace the recirculation pump assembly. This may involve draining the unit and disconnecting unions.
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Repair Difficulty

Hard 4/5

Required Part

Recirculation Pump
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