Bear in mind that cats are supposed to get most of their water from their food. Descended as they are from desert-dwelling cats, they do not drink much at all. If you see your cat drinking a lot, either he is sick (diabetes, kidney disease, hyper-T, etc.) or he's eating a diet primarily of kibble. If it's the latter, consider switching to canned food. Even the lowest quality canned food is better that so-called "super premium" kibble.
If the cat is eating canned food and is still doing this, I would get bloodwork done to rule out illness.