The toilet fill valve controls the water level in toilet tanks. Water stored in the tank empties into the bowl when the lever is activated, flushing waste into the sewer. After the tank drains, the toilet fill valve automatically refills the tank.
Located in the tank on the left-hand side, the toilet fill valve apparatus resembles a circular tower with the valve located on top of the tower. Water flows from the valve to replenish the tank. This is controlled by the float ball, which attaches to the fill valve by a metal rod. The float ball rises as the water level rises, forcing the rod into the fill valve. When the rod contacts the switch, the valve shuts off. When the float ball lowers even a little bit, the rod loses contact with the switch and the valve opens and starts filling the tank.
Water level, and therefore flushing power, can be adjusted by bending the metal float ball rod up or down. Higher water levels mean greater flushing power, but also larger water usage. Lower water levels translate to less flushing power and less water usage.