And a mystery solved. Our cats have their own bowl of water in their room next to their food dish. Always full, replaced twice a day. However, the dogs water bowl is apparently where the good stuff is. I have to fill up the bowl three times a day to keep up with demand. Cats seem to prefer dog water. ?... Anyway I've noticed a ritual the cats perform before they drink...they rub the bowl. Cat claws on stainless steel bowl makes an irritating noise. Finally figured out the bowl rubbing is to try and move the water bowl off of an astroturf mat that we feed the dog on...because the mat tickles their feet. Only took six months to figure that one out. Now as to why dog water is better than cat water?