Drinking Water—Safety on Tap - Public And Private Water Supplies

Public Water Systems

According to the Environmental Protection Agency's (EPA) April 2003 fact sheet Public Drinking Water System Programs, public water supply systems serve 85% to 90% of the U.S. population. The remainder gets its water from private water systems. Urban areas draw their supplies largely from surface water sources, while 90% of the drinking water in rural areas is drawn from groundwater.

A public water supply system is one that has at least fifteen service connections or serves at least twenty-five people per day for sixty days of the year. According to the EPA report Factoids: Drinking Water and Ground Water Statistics for 2003 (January 2004), there were 161,201 of these systems of varying size in the United States in 2003. The amount and type of treatment provided varies with source and quality. For example, some public systems using a groundwater source require no treatment, while others may need to disinfect the water or apply additional treatment.

There are three types of public water systems. Community water systems are those that supply water to the same population year-round. In 2003 there were approximately 53,363 community water systems serving 273 million people in the United States, or more than nine out of every ten Americans. (See Table 5.1.)

Non-transient non-community water systems are the second type. They serve the public but not the same people

TABLE 5.1
Types of public water systems, by water source and population served, 2003 Population Percent of Percent of Water source Systems served systems population
SOURCE: Adapted from "Water Source," in FACTOIDS: Drinking Water and Ground Water Statistics for 2003, U.S. Environmental Protection Agency, January 2004, http://www.epa.gov/safewater/data/pdfs/factoids_2003.pdf (accessed April 11, 2005)

year-round. Examples of non-transient non-community systems are schools, factories, office buildings, hospitals that have their own water systems, and other public accommodations. There were 19,686 non-transient noncommunity water systems in the United States in 2003 serving 6.3 million people, or roughly 2% of the population. (See Table 5.1.)

Transient non-community water systems are the third type of public water system. These are systems that provide water in places such as gas stations or campgrounds where people do not remain for long periods of time. In 2003 there were 88,152 such transient non-community water systems serving 23.3 million people, or about 8% of the population. (See Table 5.1.)

The EPA and state health and environment departments regulate public water supplies. Public suppliers are required to ensure that the water meets certain government-defined health standards under the Safe Drinking Water Act (SDWA; Public Law 93–523). This law mandates that all public suppliers test their water on a regular basis to check for the existence of contaminants and to treat their water supplies, if necessary, to take out or reduce certain pollutants to levels that will not harm human health.

According to the EPA report Factoids: Drinking Water and Ground Water Statistics for 2003, 94.5% of public water systems (152,405) are small or very small, each serving fewer than 3,300 people. (See Table 5.2.) The remaining 5.5% of systems are few in number (8,796) but service many more people. The medium size services each provide water to between 3,301 and 10,000 people. The large services provide water to more than 10,000 people each. Together the medium and large public water services provide water for the vast majority of Americans who drink water from a public supply: 262,672,363 people.

Private Water Systems

According to the EPA's Drinking Water Standards & Health Effects (December 1999), 10% of Americans receive their water from private wells. System owners are solely responsible for the quality of the water provided from these sources. Individual wells serving four or fewer housing units provide the water for approximately 15% of homes. Only 1% of the nation's homes get their water directly from another source, such as creeks, rivers, lakes, springs, and cisterns.

Personal private water supplies, usually wells, are not regulated under the SDWA. Many states, however, have programs designed to help well owners protect their water supplies. Usually these state-run programs are not regulatory, but provide safety information. This type of information is vital because private wells are often shallower than those used by public suppliers. The more shallow the well, the greater the potential for contamination.