The Type FSG - PUMPTROL Water Pump Pressure Switches are used to control electrically driven water pumps, suitable for all types of pumps: jets, submersible, reciprocating, etc. Square D Pumptrol Water pressure switches are ideal for rural customers who usually rely on wells to supply their water. Pumps are used to bring up the water from the well and to pressurize the water pipes in the home. Water is pumped into a storage tank to compress an air bladder that exerts pressure on the water in the home. When the desired pressure is reached, the pump must be stopped. This is where the pressure switch opens a set of electrical contacts to stop the pump. When water is used, the pressure in the storage tank falls. When the lowest desired pressure is reached, the switches close to start the pump and recharge the system pressure.