IS BOTTLED BETTER? Bottled water isn't necessarily safer than tap water. The FDA merely requires manufacturers to meet the basic tap water standards set by the EPA, so purity largely depends on the brand. Anyone with a compromised immune system should read the labels of bottled water carefully to make sure it is sufficiently purified for their protection.
WHERE THAT GLASS OF WATER COMES FROM: Drinking water comes from either ground water sources (via wells) or surface water sources such as rivers, lakes, and streams. Most U.S. water systems in small and rural areas use a ground water source, while large metropolitan areas tend to rely on surface water. Causes of contamination can range from agricultural runoff to improper use of household chemicals.
SECONDARY STANDARDS: Even if your tap water meets the EPA's basic requirement for safe drinking water, some people still object to the taste, smell, or appearance of their water. These are aesthetic concerns, however, and therefore fall under the EPA's voluntary secondary standards. Some tap water is drinkable but may be temporarily clouded because of air bubbles, or have a chlorine taste. A bleachy taste can be improved by letting the water stand exposed to the air for a while.
The American Physical Society and the Materials Research Society contributed to the information contained in the TV portion of this report.