Once upon a time...
...I worked in a medium sized college. It was of the kind where undergraduate students actually lived on site, and The "IT Department" such as it was was located in what had once been a professors apartment on the ground floor of one of the accommodation blocks.
The server room was located in what had originally been the shower block for that floor when the building was put up back in the 60s before it was re-fitted so that each student room had their own toilet/shower room somewhere in the late 90s. This was actually a remarkably good idea, because it meant that the floor contained a high capacity drain, and the room had huge amounts of ventilation that was perfect for putting a nice big AC unit up to, and any run-off could simply go down the hole in the middle of the floor. It also meant that should the fire suppression system ever actually go off, it wouldn't flood.
This setup all worked out very nicely until one day the accumulation of hair and other... waste products... produced by showering students blocked up the drainage pipes and it was discovered that the retro-fit job hadn't been of the highest quality.
Everything drained in series, and once one blocked up, everything "up stream" of that would block up too. This wasn't immediately obvious to the students in question, because the shower drainage pipes ran through the drop ceiling of the floor below and snaked back and forth so they could cover all the rooms. This meant that there was actually a pretty large storage capacity in all the pipework.
I think you can see where this is going. Over the course of a weekend all the students upstairs were happily showering away and that large pipe was filling up with water as the blockage at the far end prevented it from draining. Eventually water started coming back up through the floor and into the shower cubicles - but we're dealing with undergraduate students here, and they're used to living in crappy accommodation where that sort of thing happens, so most of them just ignored it.
Then the pipe burst.
Directly over the server room.
...and about three days worth of accumulated filthy waste water got dumped out straight onto the top of a rack full of hardware that all immediately went "Bang"