EPA Public Drinking Water Systems: Facts and Figures

EPA Topics > Water > Drinking Water > Drinking Water System > Drinking_Water_System_sites.htm > Public Drinking Water Systems Programs > Water System Facts and Figures, 2001 (www.epa.gov/safewater/pws/factoids.html)

There are approximately 170,000 public water systems in the United States. EPA classifies these water systems according to the number of people they serve, the source of their water, and whether they serve the same customers year-round or on an occasional basis. The following statistics are based on information in theSafe Drinking Water Information System(SDWIS), for the fiscal year ended September 2000, as reported to EPA by the states.

For more detailed statisticson public drinking water systems and violations of drinking water rules, readFactoids: Drinking Water & Ground Water Statistics for 2000(PDF file, EPA 816-K-01-004)[help with PDF files]or investigategetting access to drinking water data.

Classifications:

Public water systemsprovide water for human consumption through pipes or other constructed conveyances to at least 15 service connections or serves an average of at least 25 people for at least 60 days a year. EPA has defined three types of public water systems:

Community Water System(CWS): A public water system that supplies water to the same population year-round.
Non-Transient Non-Community Water System(NTNCWS): A public water system that regularly supplies water to at least 25 of the same people at least six months per year, but not year-round. Some examples are schools, factories, office buildings, and hospitals which have their own water systems.
Transient Non-Community Water System(TNCWS): A public water system that provides water in a place such as a gas station or campground where people do not remain for long periods of time.

EPA also classifies water systems according to the number of people they serve:

Very Small water systems serve 25-500 people
Small water systems serve 501-3,300 people
Medium water systems serve 3,301-10,000 people
Large water systems serve 10,001-100,000 people
Very Large water systems serve 100,001+ people

Number of Systems and Population Served for 2000:
(note: populations are not summed because some people are served by multiple systems and counted more than once)

54,064 CWS served 263.9 million people
19,738 NTNCWS served 6.9 million people
93,210 TNCWS served 12.9 million people

Community Water System (CWS) :

Source of water:

11,403 systems relied on surface water, serving 178.1 million people
42,661 systems relied on ground water, serving 85.9 million people

System size:

15% of CWS are very large, large, or medium, serving 90% of those who get their water from a CWS
85% of CWS are small or very small, serving 10% of those who get their water from a CWS

Non-Transient Non-Community Water System (NTNCWS) :

Source of water:

821 systems relied on surface water, serving 932,000 people
19,738 systems relied on ground water, serving 6.0 million people

System size:

99.4% of NTNCWS are small or very small, serving 76% of those served by NTNCWS
0.6% of NTNCWS are medium, large, or very large, serving 24% of those served by NTNCWS

Transient Non-Community Water Systems (TNCWS) :

Source of water:

1,912 systems relied on surface water, serving 917,000 people
91,298 systems relied on ground water, serving 12.0 million people

System size:

99.8% TNCWS are small or very small, serving 78% of those served by TNCWS
0.2% of TNCWS are medium, large, or very large, serving 22% of those served by TNCWS

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