Display shows “Err 18” and unit indicates resin sensor or quality sensor error (advanced models)

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.

Possible Causes

Sensor fouled by iron or manganese, Sensor cable damaged, Sensor out of calibration, Control board sensor input failure

Safety: Depressurize the system before removing any in-line sensors.

Clean sensor: Remove the resin quality sensor from its port and soak in a mild cleaning solution suitable for iron/manganese removal. Rinse thoroughly.
Inspect cable: Check the sensor cable for cuts or crushed sections. Reseat the connector at the control board.
Recalibrate: If the model supports sensor calibration, follow the Ecowater procedure using known soft water.
Replace if needed: If Err 18 remains after cleaning and recalibration, replace the sensor assembly.

Medium 3/5

Ecowater resin quality sensor

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