I really don't know what may be wrong with your poor Pop. I do know that if a human starting drinking too much or in the case of my dad's dog some years ago, it can be the first signs of diabetes or kidney trouble, I would be inclined to arrange a vet check for kidney problems, I guess this may mean trying to obtain a urine sample

maybe someone on the forum can help you with how to do this. Let us know how things go.
