Bottle water, including carbonated soft drinks, fall under two regulations:  21 CFR Part 129 and 21 CFR Part 165.110. Bottled water, according to 21 CFR Part 129, must come from an approved source of water. Approved source is defined as a source of water that has been properly inspected and found to be of safe and sanitary quality. All treatment of bottled water must be done in accordance with the regulation of the Federal Food, Drug, and Cosmetic Act.

Proper sampling of water from its source must be conducted as often as necessary or at a minimum of once every year for chemical contaminants and once every 4 years for radiological contaminants. Water collected from any source other than a public water system such as springs, artesian wells, or drilled wells must be tested for total coliform at least once each week. Source water found to contain Escherichia coliis not considered to be of safe or sanitary quality and cannot be used for bottled water until it has undergone the proper testing and safety measure to ensure it is negative for E. coli. 

Helpful FDA links include:

Bottle Water/Carbonated Soft Drinks Guidance Documents & Regulatory Information

Small Entity Compliance Guide:  Bottled Water and Total Coliform and E. coli