What would happen if everyone on Earth flushed at the same time? And how does toilet flushing work, by the way? When you flush your toilet, you don’t even give a second thought to what happens to sewage water in the pipe work: how fast it travels, or where it goes. But if you ever do, then you should hope there will never come a day when everyone in the world flushes at the exact same moment.

In older buildings, especially outside the US, you can still find this kind of a drawer that opens up on a really huge vertical pipe. That’s where all the waste goes when you and your down and upstairs neighbors flush. May sound gross, but you can even hear the waste water rushing past you when someone above presses the button. So imagine that the whole column just decided to flush at the exact same moment...

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