If your drinking water supply comes from a well, it would be advisable to test it for pollutants. Contact your local health department personnel for a list of the typical well water contaminants in your area. You may want to get your drinking water tested by an independent lab.
Look under "Water Analysis" in your yellow pages or ask your local or state health department for names of certified laboratories that can analyze your well water for bacteria, nitrates, hardness, iron, sediment, radon, arsenic, and even pesticides. Once you know contaminants are present, you can address each issue with an appropriate treatment.