I’ve recently noticed water in my colony, and I found that this water basin was leaking slowly. [Edit: The white tiles were built after the fact to stop the leakage. Before that the water was just contained by the natural tiles you see.]
I don’t think the game explains this at all, so I’m asking here: Which materials allow water to pass through them, and which don’t?
Is there an animation of that? I don't recall ever seeing that mechanic at play, but I'm a few years since my last playthrough.
Yes, there is. The liquid was very obviously dropping from the ceiling of the room below. Unfortunately, I don’t have a screenshot of that.