for your cats that is. How often do you change out all the water. I feel guilty somehow that I'm not changing the water. Edwina likes it now. She even drinks out of the water as it comes down the water fall.

I have a Petmate Fresh Flow. (And please don't tell me to read the owner's manual! I haven't a clue where it is now and anyway..that doesn't seem sporting!) I keep it filled up -- either the tank or directly into the bowl -- and it has a filter.