The Basic Concept Behind the Flushing Toilet

Flushing a toilet is the perfect example of basic physics. A toilet is little more than a storage tank of potential energy. The tank on the back of every toilet, as most people know, is filled with water.

When the flushing lever is pressed all of the stored water in the tank is suddenly released through a hole in the bottom of the tank. The water is guided through same angled holes in the top of the bowl in order to create a whirlpool effect. The bowl of the toilet is filled very quickly. The energy at this time is all converted into kinetic energy.

picture borrowed from: http://www.toiletology.com/howitwrk.shtml

From here the process is basically repeated, though this time it is of more importance. The bowl of the toilet has built into its bottom a pipe know in the plumbing world as a p-trap. This pipe goes straight down from the bowl curves back up behind itself, and bends down again. When the bowl is quickly filled with enough water, there is enough potentail energy and momentum in the bowl to push some of the water through the p-trap. This p-trap then causes a siphon on the other side which then sucks the rest of the water and anything else from the bowl