Despite claims made by a salesperson that your drinking water is unsafe, local authorities closely monitor water treatment plants to assure that only safe drinking water is available. If you doubt that your water supply is safe, your water can be tested.
The Environmental Protection Agency (EPA) regulates the water purification industry and water purifiers must comply with EPA standards. The EPA's drinking water hotline (800-426-4791) can provide a list of certified water testing labs. Purifiers can remove organic chemicals and soften hard water but cannot remove bacteria to make water safer.