The operation of most toilets depends on gravity. Water is stored in the toilet tank, which is mounted above the level of the toilet bowl. Most of the mechanics of the toilet are mounted within the tank. A water supply hose is connected to the bottom of the tank to keep a one-flush supply of water ready to be used the next time the flush handle is depressed. A rubber flapper or stopper at the bottom of the tank seals the water supply held in the tank from entering the toilet bowl until the flush handle is depressed.
The toilet bowl has two main functions. It carries waste down the sewer drain and also has a built-in trap that keeps sewer gas from entering the home. The trap also keeps the bowl filled with water for the next use. The force of water needed to flush all the waste in the bowl down the drain is provided by gravity from the toilet tank. The toilet bowl and tank are attached together with rubber seals and brass bolts.
Flushing the Bowl
The stopper at the bottom of the toilet tank is lifted when the flush handle is depressed. This empties the water from the tank into the bowl with enough force -- creating a siphon -- to flush the contents of the bowl through its trap and down the drain. When the flush handle is released the rush of water into the bowl and down the drain stops, and the tank stopper falls back into place.
Refill the Tank
A mechanism in the tank -- called a ball-cock -- detects when the water in the tank goes below a certain level. As the water leaves the tank, a float-ball trips the ball-cock. This triggers the ball-cock to turn on the water supply to refill the tank. When the water reaches a certain height, the float ball -- which floats at the top surface of the water level -- triggers the ball-cock to shut off the flow of water.