Suddenly today, out of nowhere, I found myself mystified by how a toilet works. I feel like I have a pretty good grasp of what’s happening in the tank, in other words, the mechanical part of the toilet. There’s a valve to let water in, and a float-operated shutoff to cut the water when it gets to a certain level. When you push down on the handle, the attached chain lifts the gaskety thing in the bottom of the tank, allowing the water to suddenly drain into the toilet bowl through holes in the rim.
But here’s where things get mysterious to me. At the start, there’s a certain water level in the bowl. The first thing that happens when you flush is that water surges in from the tank, sending the water level temporarily higher. But then the water in the bowl doesn’t just fall back to its original level, it more or less completely empties, before slowly refilling.
So what accounts for the force that causes the bowl to empty, taking everything with it? And what determines the baseline water level in the bowl between uses? The physics of the whole things eludes me (as well it might, since my knowledge of physics would fit comfortably in a thimble).