Most bottled water is treated with the same chemicals, except fluoride, that tap water is treated with if I remember correctly. You'd also incur less expenses in terms of buying large quantities of soda and water. Tap water is safe to drink and provides your body with many other minerals and nutrients that bottled water does not provide.
If you still think that tap water will murder you and your entire family, then go keep drinking soda. I hope you'll be happy when your teeth begin to rot beyond repair. Or buy distilled water.