As it's been explained to me, spring water and other bottled waters are very similar to tap water - it's just that they are "tapped" at a different location. But, it can have the same problems as tap water. Now, these are my naturalistic, co-op buying, hybrid driving friends that tell me this, so it could be a bit of an alarmist position. However, I buy distilled water and use that for my LOs bottles. Since she's 6MO she needs flouride and my ped gave me a perscription for a flouride vitamin to add to her water (our tap isn't flouridated either). There is a product called Nursery Water that is distilled and has flouride added, but it can be like $2 a gallon.
I would call your pediatrician and get clarity from him - on the bottled v. distilled water and on the flouride item as well.