He if likes it, it might not be a bad idea ... as far as I can tell the more that cats drink, the less likely they are to to have blockages. At any rate, anytime I've known someone with a cat with stone problems, their vet has been insistent on getting the kitty to drink more.

And, fwiw, there's at least one local cat specialist who suggests cranberries as being good for some cats with stone probs ... you need to know whether the stones are alkaline or acid produced, if the former then cranberry extract helps, if the latter, then not.