I have been looking at the Drinkwell fountains on Amazon. I keep 2 large ceramic bowls of water out for the cats and change it at least once, usually twice a day but my concern is when we go away for a few days, even though I have someone to come and feed them and I ask them to change the water daily, I'm guessing that they probably just look to see if there is water and leave the same water. The fountains filter the water and keep it moving so it doesn't get stagnant. There are several different drinkwell models, some with larger reservoirs to hold more, which you might need for 4 cats. I was thinking of the platinum.