We covered the Clean Water Act in a previous post. The Safe Drinking Water Act is the Clean Water Act’s counterpart, regulating the treatment of drinking water in the US. The Safe Drinking Water Act (SDWA) is the main federal law that ensures the quality of Americans’ drinking water, originally passed by Congress in 1974 to protect public health by regulating the nation’s public drinking water supply. The law was later amended in 1986 and 1996. The SDWA applies to every public water system in the United States. There are currently more than 170,000 public water systems providing water to almost all Americans at some time in their lives. Private wells and bottled water are not regulated by the SDWA.
Originally, the SDWA focused primarily on treatment as the means of providing safe drinking water at the tap. In 1996, the act was revisited, and the resulting amendments greatly enhanced the existing law by recognizing source water protection, operator training, funding for water system improvements, and public information as important components of safe drinking water. This approach ensures the quality of drinking water by protecting it from source to tap.
There are a number of threats to drinking water, such as: improperly disposed of chemicals, animal wastes, pesticides, human wastes, wastes injected deep underground, and other naturally-occurring substances. Likewise, drinking water that is not properly treated or disinfected, or which travels through an improperly maintained distribution system, may also pose a 
health risk. To ensure that drinking water is safe, SDWA sets up multiple barriers against pollution. These barriers include: source water protection, treatment, distribution system integrity, and public information. Public water systems are responsible for ensuring that contaminants in tap water, such as microbial contaminants and disinfection byproducts, do not exceed the acceptable standards. Water systems treat the water, and must test their water frequently for specified contaminants and report the results to states.
The EPA has set standards for 90 chemical, microbiological, radiological, and physical contaminants in drinking water, and is currently conducting research and collecting information under round three of the Unregulated Contaminant Monitoring Rule (UCMR3) to determine which currently unregulated contaminants pose the greatest public health risk and will therefore be regulated in the future. American Water College and Eurofins Eaton Analytical offer sample collection training for UCMR3, which is available at no cost.