Have you ever noticed that bottled water has an expiration date? I have to admit, I'm a little rigid when it comes to expiration dates. Once a date has passed, I chuck it, even if it's only a few days after the expiration date has passed. But unlike mayonnaise, bottled water doesn't seem like it needs an expiration date. It's just water!
What's up with that?
Blame New Jersey. (And I say that as a former New Jersey resident.) New Jersey requires bottled water to have expiration dates, so instead of having a separate run just for the Garden State, bottled water manufacturers found it simpler to put expiration dates on all water bottles. Even if the water doesn't go bad, the information helps identify the bottling plant and date when it was bottled in case there's a need to isolate a contaminant for a recall. And don't look to other branches of the government for answers. The Food and Drug Administration (FDA) says bottled water has an indefinite shelf life, while the U.S. Department of Homeland Security recommends that people change the water in their disaster-preparedness kits every six months.
It should be noted that even though the water itself doesn't go bad, the plastic from the bottle could begin leaching chemicals after a long period of time. They're not necessarily harmful, but they will alter the taste of the water somewhat. (The expiration date also helps the manufacturer in this scenario if a customer calls to say the water tastes bad and it's a year past the expiration date.)
In addition, it matters where you store the water. Many people where I live in Florida store their water in the garage. The problem with this is that it can expose the water to extreme temperature changes, and that can affect water quality. So if you want to stockpile water for an emergency, it's better to store it inside the house where the temperature is more stable.
A recent study published in Environmental Pollution conducted by University of Florida researchers found that water left in hot environments for a prolonged period of time had increased amounts of potentially harmful chemicals. It's for this reason that occasionally drinking a hot water bottle left in your car overnight is probably fine, but doing it regularly is not recommended.
It's also worth mentioning that contrary to popular belief, bottled water is not necessarily better for you than tap water. Tap water is regulated by the Environmental Protection Agency, while bottled water is regulated by the FDA. Tap water in the United States goes through a strict regulation process, filtered tap water is still your best bet when it comes to your health and reducing your carbon footprint.