No, properly stored bottled water does not expire

Hydration is important when it’s hot outside. During the summer, many people prepare themselves by keeping bottles of water somewhere they might come in handy during an emergency.

Readers have asked VERIFY about bottled water expiration dates, the safety of water left out in the heat and whether water is still good to drink once it’s been opened for a few days.

THE QUESTION

Does bottled water that’s properly stored expire?

THE SOURCES

THE ANSWER

No, government food safety agencies say bottled water that has been properly stored and is unopened does not expire. 

WHAT WE FOUND

Foodsafety.gov, which is run by a partnership of the Food Safety and Inspection Service (FSIS), the FDA and the Centers for Disease Control and Prevention (CDC), says commercially bottled water can be stored indefinitely if in the pantry from the date of purchase.

“Water will store indefinitely, though the taste may be impacted by storage conditions, including sunlight, items stored around it and the containers being used to store it,” foodsafety.gov says.

Many manufacturers give their bottles two-year expiration dates anyway, not because of safety reasons but because of taste, the New York State Department of Health says. 

But again, this specifically applies to unopened bottles of water that have been properly stored. The IBWA recommends storing water at “room temperature or cooler, out of direct sunlight and away from solvents and chemicals such as gasoline, paint thinners, household cleaners, and dry cleaning chemicals.”

The rules are a little different for containers you fill with tap water to store for emergencies. The CDC and the Red Cross say you should replace the water in these containers every six months.

If you do have any doubts about your water, use your own common sense. If the water in the bottle smells, tastes or looks weird, you might want to throw it out, Nao Medical, a healthcare provider in the New York City area, says.

The Washington State Department of Health has a guide on what causes water to look, smell or taste funny and the risk each unusual characteristic poses to your health.

What if my bottle of water has been exposed to the heat or sun?

Our sources generally agree that any potential health risk from drinking a single bottle of water left out in heat or sun is low, especially when compared to the risks associated with dehydration in an emergency.

Some people worry about chemicals from the plastics getting into the water if a plastic water bottle has been left out in a hot car, but the experts VERIFY spoke with said that hot water bottles pose little risk.

“If I'm going to be concerned about anything, I'm going to be way more concerned about the potential for biological contamination than I am for the possibility of chemical contamination, although neither one of them I would say is an existential risk,” Carroll said.

Christopher Reddy, Ph.D., a chemist with the Woods Hole Oceanographic Institution, says that chemicals in plastic water bottles do slowly leach into the water over time, and this process is faster when the plastic is exposed to heat and sunlight.

But Reddy also said the mere presence of these chemicals does not necessarily mean they are toxic, or that there is enough of the chemical to be toxic. Ultimately, Reddy said, “it’s the dose that makes the poison.”

Studies from 2007 and 2014 found that water in plastic bottles didn’t have chemicals above EPA limits until about a month of constant exposure to the heat of a car left out in the midday summer sun.

Keep in mind the FDA believes there is no limit on the shelf life of bottled water if it’s properly stored. Water left out in the heat or sun has not been properly stored.

The IBWA does note that algae or mold may infrequently develop in water that is exposed to heat or sunlight for extended periods of time, but that isn’t a “general concern for public health.”

How long is an opened, unfinished bottle of water good for?

If you open a bottle of water, take a sip from it, and then save the rest for later, you don’t have to worry about finishing that water in a set amount of time.

“I have zero problem with someone continuing to drink from a water bottle or any other beverage they've opened,” Bob Metcalf, Ph.D., a California State University, Sacramento microbiologist who specializes in drinking water. “There might be some bacteria that would get from the mouth to the remaining water, but they are from you, microbes that aren't causing you a problem, and they won't multiply in water.”

Bill Carroll, Ph.D., a professor of chemistry at Indiana University Bloomington, agreed that microbial contamination from opening a bottle of water isn’t an “existential risk.” However, he explained that it is possible a little bit of whatever was in your mouth might wind up in the bottle and provide a medium for bacteria to grow in.

An email from the IBWA and a blog post from Mountain Valley Spring Water, a bottled water company that uses glass bottles instead of plastic, says that opened water can remain at its freshest and purest if you refrigerate it between sips.

Buxton, a British bottled water company, says your water may taste slightly different if left open because it will start to absorb carbon dioxide. “For this reason, the recommended period is to consume the water three days following the day it was opened,” Buxton says.