I have a watering system on my racks (two 6-bin racks), and love it. I have had a few rats who liked playing with the lickers and did flood their tubs, but not enough to kill any one (including on female who flooded her 2 week old litter!). (I had to cull those females. I hated doing it though. ) Other than that, I check everything at least once daily to make sure it is functioning properly. Even so, a single malfunction can result in disaster. I haven't yet modified my racks yet, but I have heard of a couple people who drill holes in the tubs and insert the lickers that way, instead of putting the lickers in through the top. This serves multiple purposes: smaller babies can reach the lickers, should a malfunction occur it will only flood up to the licker (maybe an inch, depending on where on the side of the tub you put the licker) and not the whole tub. A rat can survive in water for a period of time (I don't know the limit, but I know there's something about rats being able to tread water for days before dying, dont' know if that's accurate or not), as long as they can keep their heads above water to breath. If you are checking tubs daily, you'll be able to rescue any rats if such a malfunction occurs, especially if there's only an inch of water.