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Public Drinking
Water Systems:
Facts and Figures
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 the Safe
Drinking Water Information System (SDWIS), for the fiscal year ended
September 2000, as reported to EPA by the states.
Classifications:
Public water systems provide 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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