This explains how the siphon works to keep the bowl at the same level and to create the force of a "flush". Until I saw a toilet that had the siphon shape visibly exposed on the outside, I don't think I ever thought question how it worked. Once I saw the shape, I immediately thought about it working like a siphon I'd used to pull gas out of my car. For people who have never seen a toilet with the siphon shape exposed, they'd probably have to have siphon experience in some other area to make the leap, or I think how the bowl stays full and flushes would just naturally stay a mystery. Believing that it all happens in the tank might also be enough of an explanation for most to stop thinking about it.
As someone who just suffered through a clog recently, I liked this explanation from an MIT student better. It starts out the same, with a good diagram and a description of the basic principle, but then goes the extra mile with actual physic equations.
This explains how the siphon works to keep the bowl at the same level and to create the force of a "flush". Until I saw a toilet that had the siphon shape visibly exposed on the outside, I don't think I ever thought question how it worked. Once I saw the shape, I immediately thought about it working like a siphon I'd used to pull gas out of my car. For people who have never seen a toilet with the siphon shape exposed, they'd probably have to have siphon experience in some other area to make the leap, or I think how the bowl stays full and flushes would just naturally stay a mystery. Believing that it all happens in the tank might also be enough of an explanation for most to stop thinking about it.
http://home.howstuffworks.com/toilet2.htm