funny thing, I always drink a lot. When I teach, I need around 1 liter a day besides my usual drinks. I normally drink around 5/6 glasses of water a day, more if it is warm. I do feel thirsty. (I don't drink anything else beside water, not even coffee). My husband on the other hand drinks two glasses maybe, no more than that. My son is the same (but he has only one kidney which may be why and he does take a full baby bottle of chocolate drink at breakfast).