Board Thread:General Discussion/@comment-4556650-20130716143338/@comment-3390396-20130720110655

We should not work on the assumption that the series has made mistakes, that would lead to more and more confusions, and very close to speculation.

What I'm lead to believe is that the "Fountain of Youth" was/is the cup that holds/held the water which makes one immortal. While any person will consider a "fountain" in the usual sense of the world to be a location, it's pretty evident that in the series, it's more or less an object. It might also be that it is somewhat of a lake: the cup functions as a small lake, that has water for only one individual. What Ban did was drink the water. In a real fountain, he would have drunk a little, and the fountain would still be flowing; here, since there was enough water for only one person in the first place, there was none left after Ban drunk it. Illogical point of view, but... to me, it it the most sound one.