Ball, fill & float valves

Float valves or ballcocks as they're more commonly known are a flushing mechanism for filling water tanks. These are typically found in the cistern of your toilet. As the water tank fills up the ball float sits on the surface of the water, once the water reaches a certain point, the valve closes to cut off the water supply. As the water empties the tank during a flush, the ball float drops and the valve then re-opens to refill the tank.