My niece is 21 months and she's constantly carrying around a drink and drinking. My sister lives in the desert (Phoenix, Arizona) where it's like 120F+ most of the year so she blames it on that so she doesn't get dehydrated. But she has like probably 15 wet nappies a day, if she doesn't change her nappy for like an hour it gets soaked. And she doesn't eat much during the day and I think it's because she's constantly drinking and getting full up on juice. I personally don't think it's "normal" but my LO isn't 2 yet and doesn't drink that much.