Environmental factors, packaging and processing methods limit the shelf life of water in both opened and unopened bottles, although the United States Food and Drug Administration has no regulations regarding how long bottled water is good to drink. In general, refrigerated open bottles of water are good for about 3 days, while unrefrigerated open bottles of water only last a few hours.
The biggest contributing factor to bottled water going bad is the bottle itself. Exposure to air causes the the chemicals in the bottle to react with the water within, and this can affect the taste and consistency of the water. Effects that are possible include off-tasting water or a minimal amount of cloudiness appearing in the water.
Unopened bottles of plain water can last 2 years or more, whether they are refrigerated or not. Bottles of sparkling water can last for 1 year or longer, while flavored water or vitamin-enhanced water has a shelf life of about 9 months.