Like all packaged food and drink, bottled water is regulated by the FDA, whose position is that there’s no limit on its shelf life (provided it was bottled and stored properly).
So why does bottled water have an expiration date? Blame New Jersey. A 1987 law in that state required all foods (legally, water is a food) sold in New Jersey to display an expiration date of two years or less from their date of manufacture. Because it would be inefficient to make separately labeled batches of product just for New Jersey, most bottled water producers began stamping their products with a two-year expiration date, says Stephen Kay, vice president of communications for the International Bottled Water Association. A bill repealing the requirement was signed into law in early 2006, but many large retailers like Wal-Mart now insist on expiration dates.
That doesn’t mean, however, that the bottles you’ve been storing in your basement for the Apocalypse will taste the same as those you bought last week. The plastic (high-density polyethylene, or HDPE) that makes up most bottles is slightly porous, which means the water inside can pick up smells and tastes from its environment. “The bottles are … not hermetically sealed,” Kay says. A few months or years in a musty basement will result in musty-tasting, but not unsafe, water. “I’m not aware of any issue that would make them nonconsumable,” says Dr. Sam Beattie, a food safety extension specialist at Iowa State University. But just to be cautious, you probably shouldn’t store your bottled water (or, for that matter, anything you intend to consume) near gasoline, paint, or other noxious chemicals.
As your bottles sit, there may be some migration of chemicals from the plastic into the water, but FDA spokesman Mike Herndon says the levels are “well within the margin of safety.” You may have heard about health problems caused by plastic leaching into water from bottles. However, that applies to containers that have a high percentage of polycarbonate (like many of the hard bottles people buy at camping stores to use over and over), not HDPE or PET (polyethylene terephthalate, another popular water bottle plastic).