The Safe Drinking Water Act (SDWA) is the principal federal law in the United States intended to ensure safe drinking water for the public. Pursuant to the act, the Environmental Protection Agency (EPA) is required to set standards for drinking water quality and oversee all states, localities, and water suppliers who implement these standards. SDWA applies to every public water system (PWS) in the United States. There are currently about 155,000 public water systems providing water to almost all Americans at some time in their lives. The Act does not cover private wells.