By design, you should only be able to mop up a liquid if there is 150 Kg or less in that tile. However, if you have a flooding situation and you get the mop command issued before the tile reaches 150 Kg, it will remain no matter how much liquid ends up in the tile. For example, in the attached picture, there were 2 full tiles of polluted water. I dug out the tiles around it and then attempted to mop it up once it spread out, not really thinking about how much there would be. It should have been too much (333 Kg per tile now) however 1 tile was able to get the mop command before it exceeded 150 Kg. A dup then went in and mopped up almost the entire 2000 Kg because it kept spreading into their mop zone. Note that the liquid bottles already present were from doing as much cleanup as I could before digging.
Instead, if the amount of liquid exceeds the limit after the mop command has been issued, the command should be cancelled.
Apologies to anyone quietly enjoying this exploit,
Issue a mop command on a small amount of liquid. Then increase the liquid volume beyond what should be the limit (150 Kg). Note that the mop directive does not get cancelled and all liquid in that tile along with any other liquid that spreads into that tile is mopped up regardless of the new volume.