Pump control SHT 217 The SHT 217 is a plug-in pump control unit that switches on a connected water pump when a certain water level is reached and switches it off again after an adjustable follow-up time of 0 to 100 seconds after the sensor has dried. An acoustic and visual warning signals the presence of water. A safe and defined switch-off behavior can only be achieved with mini float switches (SHT 227).