A fill valve is a crucial component in a toilet's flushing system. It controls the flow of water into the toilet tank after a flush. When the tank empties, the fill valve opens to allow water to refill the tank to a predetermined level, ensuring the toilet is ready for the next use. Typically located on the side of the tank, the fill valve is connected to the water supply line. It features a float mechanism that rises with the water level, signaling the valve to close once the tank is full. Proper functioning of the fill valve is essential for efficient toilet operation and water conservation.