Most people don't realize that bottled water has an expiration date. In fact, it's typically only about two years from the bottling date. After that, the quality of the water can start to degrade. So, if you're storing bottled water in your garage, it's best to check the expiration date and rotate out any bottles that are past their prime.
Even if the water is still technically safe to drink after its expiration date, it may not taste as fresh as it did when it was first bottled. So, if you're planning on using your stored water for emergency purposes, be sure to give it a taste test before relying on it in a pinch.