According to the Beverage Marketing Corp., Americans drank more than 7.3 billion gallons of bottled water in 2005, more than 24 gallons per person per year, placing it second only to carbonated soft drinks as the most consumed beverage. And among the most important reasons we drink bottled water is that we're afraid of getting sick from tap water.

Q. Is bottled water safer than tap water?

A. "Tap water is far better regulated and treated than bottled water. You are entirely in the hands of the manufacturer when you drink bottled water," says Tim Ford, a microbiology professor at Montana State.

James M. Symons, aka Dr. Water, believes that if you're drinking it because of a taste or preference issue, that's understandable. If you think you're drinking safer water, you're misguided.

Q. Is bottled water from better sources, and does it have better treatment?

A. Often yes, says Symons, but the risk level of tap water is trivial. "Bottled water was started because of snob appeal and because people don't trust the government. And the fact that bottled water has become so popular is a real embarrassment to water municipalities that work so hard to keep water safe and clean."

Q. Is bottled water regulated?

A. Bottled water is regulated by the Food and Drug Administration, which adapts the guidelines set by the Environmental Protection Agency. But while the EPA does extensive testing of the municipal water supply, bottled water is rarely tested.

Aaron Margolin, a professor of microbiology at the University of New Hampshire, found no microbial difference between bottled water and water taken from a New York City water fountain. Bottled water regulations have become more stringent; you can view the guide to regulations on www.bottledwater.org, the International Bottled Water Association's Web site. The organization has set standards equal to those of the EPA.

Q. Is it true that bottled water doesn't have enough fluoride to prevent cavities?

A. Many communities have elected to add fluoride to drinking water to prevent tooth decay, though some groups oppose this practice, believing it's detrimental to health. It's important to consider supplemental fluoride from your dentist or doctor if you're drinking exclusively bottled water — particularly for children.

Q. Where does bottled water come from?

A. Some bottled water really does come from springs, but as much as 25 percent of expensive water is just filtered tap water. Anything marked "purified" or "drinking water" is likely pulled straight from the tap. Check the label for clues as to the source of your bottled water. And while the FDA doesn't regulate terms like "glacial" or "crystalline," it does regulate terms like "spring," "artesian" and "mineral."

"Frankly, most tap waters are just as good as these other types of water. ... If I had a choice, I'd drink uncontaminated groundwater (spring water), but frankly, it's beginning to cease to exist. Most groundwater in the U.S. has some level of contamination — from pesticides to microbes. A point-of-use water filter can improve the taste and microbial quality," Ford says.

Q. What is the shelf life for bottled water?

A. Bottled water is considered to have an indefinite shelf life if it is produced in accordance with current good manufacturing practices and is stored in an unopened, properly sealed container. Therefore, the FDA does not require an expiration date.

Charles Stuart Platkin is a nutrition and public-health advocate, and author of "Breaking the FAT Pattern" (Plume, 2006). Sign up for the free Diet Detective newsletter at www.dietdetective.com.