How much water is he drinking?
Has it just started?
Does he pee more than usual?
Is the pee a steady stream, what colour is it and is he straining?
You say he sleeps a lot but is he lethargic all the time or does he get lively when he wakes up?

Definitely need more info please.

If a dog is drinking excessive amounts of water there are lots of reasons, could be behavioural, UTI, Addisons, diabetes, kidney problems amongst others.

If in doubt its always best to get the dog checked out by a vet.