Pumping of water into a tank is accomplished by motor operation. When the tank is about to be full with water, the motor pump is about to stops to operate. When the tank is about to be emptied, the motor pump will start to operate. Float Switch Motor Pump Control Operation Figure below (A) shows a tank half filled with water. The motor pump M at idle condition. Water flows out from the gate valve L. Lever C is tilted downward to the right because of the weight W1. Mercury B is at the right position inside the glass container A. the metal rods X and Y inside the sealed glass container A are at open condition. Float bulb K float over the water J inside the tank. Float bulb K goes down as the water drops down. (A) Water is withdrawn from the tank. Water level drops downward. When the water level drops down beyond the stopper E, Figure below (B) the stopper E prevents float bulb K to go down further. When the water level goes down further weight W2 the effect of the combined weight of flo...