system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why does toilet water move when it's windy outside?

I live on a condo and noticed that the water in the toilet bowl was slightly moving (kinda like waves) and was fascinated. So i started paying attention to it more and noticed that it would do that only on windy days, the windier it was, the more it moved and would sometimes start to resonate which blew my already blown mind!
gpt
There is a vent that goes through your roof and is connected to your plumbing drains. It facilitates the water draining to the sewer or septic. Wind blows over it and creates oscillations in the connecting plumbing.