I've only actually "seen" my snake drink water twice.
First time was after I was holding him and I put his head into the water, I think that might have been the first time he had seen it cuz he drank a lot of it. Second time I randomly saw him drinking at night.
I know for the most part people don't see thier snakes actually drinking cuz they do it at night, when we're sleeping.
Not sure what the more experienced people on here think but I would suggest when you handle him for the first time, show him the water yourself by putting his head in it. Even if he doesn't drink right then, he should be able to know where he can come and get some later.