The Safe Drinking Water Act (SDWA, 1974) is the main federal law that ensures the quality of drinking water in the Unites States. When implemented, it extended coverage of federal drinking water standards to all public water supplies. Previous standards, established by the United States Public Health Service beginning in 1914 and administered by the United States Environmental Protection Agency (EPA) since its creation in 1970, had legally applied only to water supplies serving interstate carriers (e.g., planes, ships, and rail cars engaged in interstate commerce). However, many states and municipalities complied with them on a voluntary basis. Under the SDWA, public water supplies were defined as those publicly or privately owned community water systems having at least 15 connections or serving at least 25 year-round customers or non-community water supplies serving at least 25 non-residents for at least 60 days per year.

The SDWA required the EPA...