When we buy a bottle of water, what we're often buying is the bottle itself, as much as the water. We're buying the convenience: A bottle at a 7-Eleven store isn't the same product as tap water, any more than a cup of coffee at Starbucks is the same as a cup of coffee from the Krups machine on your kitchen counter. And we're buying the artful story the water companies tell us about the water: where it comes from, how healthy it is, what it says about us. Surely, among the choices we can make, bottled water isn't just good -- it's positively virtuous.Except for this: Bottled water is often simply an indulgence, and despite the stories we tell ourselves, it is not a benign indulgence. About 1 billion bottles of water a week are moved around in ships, trains and trucks in the United States alone. That's a weekly convoy equivalent to 37,800 18-wheelers delivering water. (Water weighs 8 1/3 pounds a gallon. It's so heavy you can't fill an 18-wheeler with bottled water -- you have to leave empty space.)