There are approximately 160,000 public drinking water systems in the United States. Each of these systems regularly supplies drinking water to at least 25 people or 15 service connections. Beyond their common purpose, the 160,000 systems vary widely. The following tables group water systems into categories that show their similarities and differences. For example, the first table shows that most people in the US (268 milion) get their water from a community water system. There are approximately 54,000 community water systems, but just seven percent of those systems (3,797) serve 81 percent of the people. The second table shows that more water systems have ground water than surface water as a source--but more people drink from a surface water system. Other tables break down these national numbers by state, territory, and EPA region. This package also contains figures on the types and locations of underground injection control wells. EPA and states regulate the placement and operation of these wells to ensure that they do not threaten underground sources of drinking water. The underground injection control program statistics are based on separate reporting from the states to EPA. The drinking water system statistics on the following pages are taken from the Safe Drinking Water Information System/Federal version (SDWIS/Fed). SDWIS/Fed is the U.S. Environmental Protection Agency's official record of public drinking water systems, their violations of state and EPA regulations, and enforcement actions taken by EPA or states as a result of those violations. EPA maintains the database using information collected and submitted by the states.