We did this in E'science. Water is the same the world over, H2O, the water cycle confirms this. I think there is probably more impurities in bottled water because it is untreated. I get amazingly cold fresh water from my taps and that's more than what some people can say in this world. A friend told me that in Hawii the people are being deprived of water because someone is bottling it and sending it around the world,
to places that have it on tap already I suppose, that is outragious
I sometimes buy bottled water but I always re-fill them then recycle the bottle. I don't think enough people do this though.