A system for provision to the public of piped water for human consumption, if such system has at least 15 service connections (such as households, businesses, or schools) or regularly serves at least 25 individuals daily for at least 60 days out of the year. Public water systems are divided into three categories:
- Community Water Systems – serves the same population year round (e.g., homes, mobile homes, housing subdivisions);
- Nontransient-Noncommunity Water Systems – regularly serves at least 25 of the same people for at least six months of the year (e.g., schools, factories, and hospitals); and
- Transient Noncommunity Water Systems – caters to transitory customers in nonresidential areas (e.g. campgrounds, motels, and gas stations).
The terms include any collection, treatment, storage, and distribution facilities under control of the operator of such systems and used primarily in connection with the system, and any collection or pretreatment storage facilities not under such control that are used primarily in connection with the system. As of 1993 there were about 200,000 public water systems in the United States regulated under the Safe Drinking Water Act (SDWA). These systems served approximately 243 million U.S. residents, or 94 percent of the total population of 258 million. The remainder of the population is served by private wells not subject to regulation under the SDWA. [Also see Appendix B–1, SDWA Regulated Contaminants and Appendix B–2, SDWA Proposed Contaminants to be Regulated, Appendix B–6, Water Treatment — Disinfectants, Appendix B–7, Water Treatment — Processes, Appendix B–8, Water Treatment — Technologies, and Appendix B–9, Threats to Water Quality.]