E18
BWT Perla
Water Hardness / Quality Sensor Fault
Display shows E18 and the unit indicates a hardness sensor or quality sensor error (if equipped)
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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
Defective inline hardness sensor, Sensor fouled by iron or manganese, Incorrect sensor wiring, Sensor not enabled or calibrated in controller
How to Fix / Troubleshooting
Safety first: Disconnect power and close valves before removing any inline sensors.
- Locate hardness sensor: Some BWT Perla models have an optional hardness or quality sensor installed on the outlet line. Identify its position and wiring.
- Inspect and clean: Remove the sensor following the manual. Clean the sensing surfaces with a soft cloth and mild detergent to remove deposits.
- Check wiring and polarity: Ensure the sensor cable is correctly connected to the designated terminal on the main PCB and not swapped with other sensors.
- Calibrate sensor: Use the installer menu to run a hardness sensor calibration, using a known hardness test kit to verify readings.
- Replace sensor if defective: If readings remain erratic or E18 persists, replace the sensor with a BWT-approved hardness sensor.
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Repair Difficulty
Hard
4/5
Required Part
Inline Hardness / Quality Sensor
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