My lab drinks water excessively which makes him urinate excessively, vet says norm for labs-ration his water.?

I suspect a possible kidney issue. His creatinine level is slightly low, but vet says not to worry, he probably has that issue poly...something or other that is supposedly common in labs where they just drink excessive amounts of water. If the dog is thirsty, shouldn't he drink? The problem is that he is urinating in the house alot even though I let him out often. Further, if there is an underlying kidney issue, I would think that the worst thing I could do is to ration his water. Not sure how to handle this-- Any lab owners that can comment on this?