A flush valve releases water from the toilet tank and into the bowl. The flush valve has a flapper that creates a water tight seal. This helps the toilet retain water until it is flushed.
The water supply comes through the wall and connects to the tank. This is regulated by a trip lever, which is triggered by the tank ball. It also cuts the water feed the moment it reaches the fill line, which is the same as the volume of the tank.
The capacity of American toilets is around 3.5 gallons of water, and this is dispelled with each flush. The flush valve connects to a flapper, a flush handle controls the flapper, and the handle lifts a chain whenever the toilet is flushed, opening the flush valve. Water flows through the valve and drains into the bowl. While the tank completely drains of water, the flapper remains open. It then closes on its own. Next, the tank ball drops while the water level rebuilds. When the water reaches the required level, the water supply is cut. This allows the toilet to be flushed again. While flushing the toilet, some of the water moves over the top of the cup in order to place it back into its space.