Old bottled water that has been sealed and stored in a cool, dark place is generally safe to drink, even years after purchase. The FDA considers properly produced, unopened bottled water to have an unlimited shelf life. The dates printed on bottles are about taste and odor, not safety. That said, how and where the water was stored matters far more than how old it is.
What Expiration Dates on Water Actually Mean
Bottled water companies add dates to their products voluntarily. These are quality markers, not safety deadlines. Over time, water stored in plastic can pick up a faint plastic, musty, or metallic taste as trace chemicals from the bottle migrate into the water. The water isn’t necessarily dangerous at that point, but it won’t taste as fresh. If your old bottle of water tastes fine, it almost certainly is fine.
The Real Risk: Heat and Sunlight
Age alone isn’t the main concern with old bottled water. Temperature and light exposure are. As plastic gets hotter, the chemical bonds in the material break down more quickly, allowing compounds like antimony and plasticizers to leach into the water at higher rates. A study from Arizona State University found that water bottles heated above 150°F showed antimony levels exceeding safety recommendations after 38 days. That kind of temperature is easy to reach inside a parked car during summer.
Sunlight accelerates the same process. UV exposure degrades plastic over time, which is why experts recommend keeping bottles in a bag or covered area rather than sitting in direct sun for long stretches. A bottle that spent two years in a cool pantry is in very different shape than one that spent a single summer in a garage or car trunk.
Chemicals That Leach From Plastic
The compounds that migrate from plastic bottles into water include antimony, phthalates, and BPA or its substitutes. These substances act as hormone disruptors in the body, and research has linked them to developmental problems in children, metabolic issues, and a possible increased risk of type 2 diabetes and cardiovascular disease. The FDA maintains that the levels typically found in food and beverage containers are safe based on hundreds of reviewed studies, but the key word is “typically.” Prolonged heat exposure pushes those levels higher.
Most single-use water bottles are made from PET plastic, which does not contain BPA. But PET still releases other trace chemicals over time, especially antimony. The amounts are small under normal storage conditions, and a single old bottle is unlikely to cause harm. The concern is more relevant for people who routinely drink water that has been stored in hot environments for extended periods.
Opened vs. Unopened Bottles
If you’re looking at a bottle that was opened and then forgotten, the calculus changes. Commercially bottled water contains no chlorine, so once the seal is broken, there’s nothing preventing bacterial growth. At room temperature, bacteria multiply quickly, and an opened bottle is best consumed within a few hours. Refrigeration slows bacterial growth significantly, but even a refrigerated open bottle should ideally be finished within a day or two.
An unopened bottle, by contrast, remains sealed in a sterile environment. Bacteria aren’t the issue with old sealed water. The only variable is what has migrated from the plastic itself.
How to Store Water for the Long Term
If you’re stocking water for emergencies or just tend to buy in bulk, storage conditions make all the difference. The CDC recommends keeping water containers at a cool temperature between 50°F and 70°F. A basement, interior closet, or pantry works well. Avoid garages, attics, sheds, or anywhere that gets warm in summer.
Keep bottles away from direct sunlight and off concrete floors (which can transfer chemicals and heat). Store them away from household chemicals like cleaning products and gasoline, since plastic is slightly permeable and can absorb fumes over time. If you rotate your emergency supply every six to twelve months, you’ll always have fresh-tasting water available, though properly stored bottles remain safe well beyond that window.
When to Toss It
You don’t need to throw out water just because it’s old, but a few signs suggest you should skip it. If the bottle has been stored in a hot environment for weeks or months, the chemical leaching is likely elevated. If the plastic looks warped, cloudy, or degraded, that’s a visible sign of breakdown. If the water tastes strongly of plastic or chemicals, trust your senses. The taste itself comes from the same trace compounds you’d rather not consume in quantity.
A bottle that has been stored in reasonable conditions, feels structurally intact, and tastes normal is safe to drink regardless of what the label says. The age of the water itself is never the problem. Plastic degradation is.