E19 error and the unit indicates a resin tank sensor or level fault (on models with resin monitoring).

Safety first: Disconnect power before accessing the resin tank sensor.

• Locate sensor: Identify the AquaSoft resin level or conductivity sensor on the resin tank or control head.
• Clean sensor: Remove the sensor and clean any iron, manganese, or scale deposits with a mild acid cleaner approved for potable water, then rinse thoroughly.
• Inspect wiring: Check the sensor cable for damage and ensure connectors are fully seated at both ends.
• Recalibrate (if supported): Use the control menu to recalibrate the sensor according to AquaSoft instructions.
• Replace sensor: If E19 persists after cleaning and calibration, replace the resin sensor module.