Thanks for the concern, MsBinky. I hadn't thought of that.
Actually, I am doing this because someone, not sure who, had sludge in their pee the other day. It hasn't happened since. They both seem fine and the vet seemed clueless, so I am trying to make them drink more and follow some things I found on the net. Ronnie and Skye both seem to like to eat and drink anything, so I don't think I should have a problem with that.