Taken from:
http://www.pressdemocrat.com/swartz/17swartz_d1prerund.html
The small water bottle is not intended to be used more than once, according to the International Bottled Water Association, a trade group for bottled water companies. The plan is for you to open the cap, drink up and, when it's empty, you put it in the recycle bin.
A spokesman for the organization agreed that it sounds like a marketing ploy to get people to buy more water, but explained it's a genuine sanitary issue. The manufacturer produces a safe bottle of water for you, following FDA regulations. But the government or the bottle maker is not there to make sure you adequately sterilize before refilling.
Some water bottlers have a tiny "Do not refill" reminder on the bottle, but most do not. Most do urge you to recycle, which is an even more important message for the industry because someone is always getting on them for stuffing the landfill with plastic.
The refill issue actually came up not with a water bottle, but with those wide-mouthed sports bottles that kids take in their lunch. When a grade school in Canada tested the kids' bottles for bacteria, they found them crawling, so much that a doctor said had they found a similar count in the town water supply, they'd shut it down.
From there the concern swung into a general suspicion of all bottles that people reuse, including the guy at work topping up his minibottle at the water cooler.
The problem is "backwash," explained a spokeswoman with Nestles Waters, which owns more than a dozen water brands, including Perrier and Calistoga. Bacteria feeds on saliva, sweat and food particles left in the bottle.
There's another concern that the thin grade of plastic can break down after multiple uses, giving the drinker something that tastes more like chemicals and less like a mountain spring.
Some scoff and say that they refill the same bottle with tap water every day when they go to the gym and again while they're there, winning points with trainers who are absolute water zealots. And they haven't fallen sick. They're probably the same ones who as kids drank from the garden hose and swallowed half the wading pool.
But that's America. You still get to choose what to obsess over. But don't say somebody didn't warn you.