Most bottled water bottles have an expiration date stamped on the bottle, but does the bottled water actually go bad? 

Some bottled water only carries its bottling date and a ‘best by’ date. These dates are helpful because the flavor of the water will change over time as it absorbs chemicals from its packaging. The flavor will not necessarily be bad, but it may be noticeable.

Leaching of chemicals from packaging is a health concern, but as far as toxic chemicals go, you can get exposure to most of those chemicals from freshly bottled water as well as bottled water that has been on the shelf a while. 

While algae and bacteria will not grow in sealed bottled water, the situation changes once the seal has been broken. One should consume water within two weeks after opening it.

Water is a natural substance and does not go bad, however the plastic water bottle will degrade over time and begin to leach chemicals into the water, which is why it is always important to choose BPA free bottled water.