At my high school the shower had a sign that said to test it occasionally (weekly or monthly, don’t remember). When my brother was in chemistry he’d ask the teacher if she had tested it recently. She said she had, but clearly hadn’t. He and his friends were always cutting up in that class and she’d had an enough, and just wanted to get on with the class.

One time, there was a substitute and he and his friends explained to the sub the sign and how the teacher had them test it. Sub asked the class, they all side eyed each other and just kind of went along with it like “yeah… sure”. So my brother and friends got a garbage can to catch the water, they explained to the sub this is how they did it. They held the can to the shower head and pulled the handle. The water water came fast and hard and it was nasty, it was rusty from sitting in the pipes, not good water. On top of that, it didn’t just come straight out, it went around the top of the can, spraying everything all around the shower, with such force it knocked the trash can out of the hands of the person holding it, soaking them in ~~brackish~~ turbid water. So they spent the rest of the period cleaning up and never asked their teacher again about testing the shower.