If you receive your drinking water from a public water system, check on the supply's quality with State or local health officials or the local water utility itself. If you are concerned about your private well or spring, have the water tested by a laboratory that is certified for drinking water testing. Try to identify which contaminants you want to test for, because unnecessary testing may be quite expensive. In most cases, the local health department will test for bacteria and they may also advise you on which other contaminants to test for. If you are interested in the quality of a specific brand of bottled water you should contact the bottler directly.
Bottlers can provide information on the required chemical analysis.