E25
Pentair Outlet Temperature Over-Limit

Heater displays E25 and shuts down during operation.

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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

Excessive outlet water temperature, Stuck internal bypass, Low flow through heater, Faulty outlet temperature sensor reading low

How to Fix / Troubleshooting

Safety: Turn off power and pump, and allow the heater to cool.

  • Verify actual water temperature: Use a reliable thermometer at the heater outlet or nearby return to confirm water temperature.
  • Check flow and bypass: Ensure valves are open and the pump is running at adequate speed. Inspect the internal bypass and thermal regulator for sticking or scale (service per Pentair manual).
  • Test outlet sensor: Compare sensor reading (via diagnostics) to actual water temperature. Replace the outlet sensor if it reads significantly lower than actual, causing the heater to overheat the water.
  • Descale if needed: If flow is good but outlet temperature rises quickly, the heat exchanger may be restricted and require professional descaling.
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Repair Difficulty

Hard 4/5

Required Part

Internal Bypass / Thermal Regulator
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