The National Institutes of Health recommends you drink six to eight 8-ounce glasses of water each day, but is the water you’re chugging—whether from the tap or bottled—healthy?

Tap water in all U.S. cities is better tested and regulated for purity than bottled water, according to the Natural Resources Defense Council (NRDC). But your tap water’s quality still depends on how well your watershed and aquifers are protected, how effectively water is treated to remove pollutants, and the condition of the pipes that bring it to your home. In a 2003 report on drinking water in 19 large U.S. cities, the NRDC concluded that only Chicago rated “excellent” for water quality; five cities rated “good,” eight were “fair” and five, “poor.”

Depending on where you live, tap water contaminants can run the gamut from bacteria to pesticides, nitrate (from fertilizers or animal waste) and even arsenic or lead. Municipal tap water is tested regularly, and its contents are published in reports enclosed with water bills. To get a copy of your report, call your local water utility or click on EPA.gov/safewater/dwinfo.htm. For help interpreting the report, go to Safe-drinking-water.org/rtk.html.

If your home has lead pipes or a private well, you might want to test your own water. Check with the EPA Safe Drinking Water Hotline, (800) 426-4791, or see www.EPA.gov/safewater/privatewells/labs.html for a list of certified water-testing labs in your state. Visit www.NSF.org to search for the water-treatment systems that are best to remove the contaminants in your water.

Keep in mind that drinking isn’t the only way you’re exposed to water contaminants. Chlorine or traces of heavy metals can be inhaled or absorbed through skin during a bath or shower. You can remove many of these with special shower filters.

Get the lead out

The Environmental Protection Agency (EPA) estimates that about 20 percent of human lead exposure comes from drinking water. Concerns have ratcheted up since late 2004, when the Washington Post reported that many cities have withheld test results showing lead levels in excess of safety standards. Lead leaches into water that stands in pipes overnight, so let your tap run 30 to 60 seconds first thing in the morning to flush that water away. Hot water leaches more lead than cold, so don’t use hot tap water for drinking or cooking. A carbon filter carafe, such as those made by Brita or PUR, will remove lead and other contaminants.

All bottled up

Because of the concerns over tap water, many people have opted instead for bottled water. Despite the paeans to purity in bottled-water advertisements, however, bottled water can’t be presumed innocent. When the NRDC tested more than 1,000 bottles of 103 brands of water in 1999, about one-third contained contaminants—including synthetic chemicals, bacteria and arsenic—that exceeded allowable limits under either state or bottled water–industry standards.