Contaminants that may cause health problems, such as nitrate, are of significant concern. For owners of private wells, the issue of ground-water contamination is particularly serious. Most private domestic supplies are neither tested nor treated on a routine basis.
Although the distinction between surface water and ground water seems simple, they are connected in such a way that surface water can become ground water and vice versa, and such surface-ground water interactions generally are difficult to observe and measure. Aquifers are often fed partially by seepage from streams and lakes. These same aquifers may discharge through seeps and springs to feed the streams, rivers, and lakes.
Private water supplies are not regulated by the U.S. Environmental Protection Agency, although some state and municipality standards apply to wells. If you have a private well, you are responsible for testing your water to make sure it is safe. This is especially important in areas where homes and nearby businesses are on septic systems. Since many contaminants are colorless and odorless, testing is the only way to determine whether your well water is safe to drink. EPA drinking water standards and health information are good guidelines for you in protecting your own drinking water.
Wells should be tested annually for nitrate and coliform bacteria to detect contamination problems early. Test more frequently and for more potential contaminants, such as radon, pesticides or industrial chemicals if you suspect a problem.