Moving the handle makes the trip lever rise. This lifts the flush ball. Water flows through the opening in the ball seat from the tank to the bowl. The flush ball drops back into place, covering the ball seat. This causes the intake valve to open.
Water entering the tank pushes the float ball up until it closes off the intake valve.
Repairs of 6 Common Toilet Tank Problems Before starting any repair, turn off the water supply valve located under the toilet tank. If there is no shutoff valve under the fixture, turn off the water at the main shutoff valve. For simple repairs you may not need to flush the water out of the tank. Only about half the float ball should be below water. When there's water in the float ball it won't rise high enough to close the valve.