Although mineral water, like other food items, is stamped with a “best before” date when bottled, its shelf life is indefinite, experts say.
The period until the expiration date is usually about a year or two. But as long as the bottle remains unopened, the water will continue to be safe to drink – as long as it was bottled hygienically, says Sebastian Rau of the SGS Institute Fresenius, a German-based provider of non-medical laboratory analysis.
Once the bottle has been opened, however, the water should be consumed within a few days. Microorganisms can enter an opened bottle, where they multiply particularly fast in light and warm conditions. Bottles that have been opened should therefore be kept in the fridge.