Most of what you flush down the toilet, ideally, is not especially dense. A few gallons of water is more than enough to make it disappear down the pipes. But if you try to flush something odd like a lead bullet, or a piece of gold (not that you should) you'll find that it just sits there. So what happens if you try to flush a dense liquid, like mercury?
Backyard chemist CodyDon Reeder of the YouTube channel endeavored to find out, though not by just pouring some mercury into the porcelain throne in his bathroom. Mercury is pretty toxic substance you don't want running through the septic system. Instead, he built a special toilet for exactly this purpose. The result is bizarre, but captivating.
It turns out mercury is not too hard to flush in small amounts, but if you get enough in the bowl to cover up the whole drain, things get tough. At that point, even plunging gets difficult, so Cody's solution was even more extreme: to fill the tank with mercury as well. The result was a successful flush that is no doubt shinier than you've ever seen.
Now I just wonder how a high abuse toilet would handle the challenge.