Bottled water advertisements often show pictures of glaciers or mountain springs to give the impression the water in the bottle is taken from a pristine source. The fact is, most bottled waters are produced in the same bottling plants supplying soft drinks (omitting the carbonation and syrups) or draw directly from local municipal water supplies. Unlike tap water, which has strict state and EPA testing requirements, bottled waters have few testing standards. The safest bottled waters are drawn from tap-water sources since those sources must meet the standards called out in the Safe Drinking Water Act. The primary value from bottled water is convenience.
Tap Water Safety Standards
Municipal water supplies have federal and (most) state mandates specifying purity of the water delivered. The Safe Drinking Water Act, EPA and state regulations define clarity as well as standards for elimination of giardia, cryptosporidium and other waterborne pathogens (disease-causing organisms). Municipal suppliers must test their water for pathogens including colliform tests hundreds of times (most states require tests every four hours) per month as well as meeting standards for disinfectants remaining in the water at the most remote taps. Even the source water (wells, lakes or reservoirs) for municipal systems must be protected.
Bottled Water Safety Standards
Bottled water sources do not have to be protected. Bottled water standards do not require a disinfection process or testing for colliforms (commonly from human or animal fecal waste), giardia or cryptosporidium. Bottled waters (excluding carbonated or seltzer waters) must test for bacteria weekly (compared to every four hours for tap water).
Is Bottled Water Unsafe?
Since most bottled waters are drawn from the bottler's local municipal supply, they are as safe as tap water. However, all bottled waters are not taken from tap-water sources and it is difficult to determine the source of most bottled waters by reading the label. Most bottled waters come from the same plants where soft drinks are bottled. Most bottlers use tap water, but run additional filtering to remove disinfectants that may affect taste, remove minerals (softening) and adjust the water's alkalinity (pH) for better mixing with soft-drink syrups. This may affect the water's shelf life.
The Cost Vs. Value of Bottled Water
A pint of bottled water costs from 200 to 10,000 times the cost of a pint of tap water. The primary value is convenience, as bottled water may be the more refreshing choice at a venue where the only alternatives are soft drinks, beer or wine. Most bottled waters are caffeine-free. For municipalities where the tap-water standards are not being met (many do not have standards for taste and smell, only safety), bottled water may offer a more palatable drinking choice.
Home Use of Bottled Vs. Tap Water
Unless your tap water is unusually hard (high mineral content) or given to periods of bad smell or taste, tap water will be at least as safe and much less expensive than bottled water. In locales where hardness, high residual disinfectant or algae tastes are concerns, a tap-mounted filter will deal with those issues. An even more cost-effective choice is to run tap water through a pitcher filter to remove chlorine and taste problems without the cost of bottled water from uncertain sources.