64000 kg liquid in one square

I'm guessing, but i'd say it's only technically in that one square, while it's actually trying to smash the tiles below it, but it can't display itself as being in those tiles until the tiles are completely destroyed.

This reminds me of another bug I found out a "long" time ago, but never reported it. I think the issue is with multiple "waterfalls", even if in this case there is just one of it.

I think what creates the hugely dense water tile is the presence of the water trapped on the left of the pump which is preventing the gas from escaping the zone, and thus water to expand. That's controversial.

Sorry for the loss of your basin tho, it's the thing i hate the most when it happens to me.

Explanation for bug in the comment:

 

Edited March 6, 2017 by HabdomeRaider