Carlo Gavazzi CD50CNF Series Capacitive Flat-Style Proximity Sensor, 10 mm Detection, PNP Output, 10 → 30 V dc,

The Carlo Gavazzi Capacitive proximity sensor is a 3 wire DC sensor. This sensor is available with open collector PNP transistor output. The sensing distance is fixed and works through a non metallic wall of up to 25 mm of thickness.

IP67 degree of protection
Basic capacitive water level sensor
Control the operation of the pump