◆ Loading atlas…

U.S. public record

The census of U.S. public water systems

143,021 active systems serving 352M people — every one an indexable public-record page, from EPA SDWIS/ECHO data.

Active systems

Very high≥ 6,000

High3,000–6,000

Moderate1,000–3,000

Lower< 1,000

Active public water systems

143,021

Population served (reported)

352M

Cumulative across systems

Community systems (CWS)

49,389

Serve residents year-round

Groundwater-sourced

90.4%

Incl. purchased groundwater

Dataset updated July 2026 . Source: EPA SDWIS/ECHO, refreshed quarterly.

Largest U.S. water systems

The 15 largest active U.S. public water systems by population served
#	Water system	State	County	Population served	Type	Source
1	New York City System	New York	Richmond	8,271,000	Community	Surface water
2	Los Angeles-City, Dept. of Water & Power	California	Los Angeles	7,751,132	Community	Surface water
3	City of Houston	Texas	Harris	2,970,543	Community	Surface water
4	Chicago	Illinois	Cook	2,746,388	Community	Surface water
5	MWRA	Massachusetts	Suffolk	2,660,000	Community	Surface water
6	Mdwasa - Main System	Florida	Miami-Dade	2,377,460	Community	Groundwater
7	San Antonio Water System	Texas	Bexar	2,113,151	Community	Purchased surface water
8	Washington Suburban Sanitary Commission	Maryland	Montgomery	1,900,000	Community	Surface water
9	Phoenix City of	Arizona	Maricopa	1,695,000	Community	Surface water
10	Philadelphia Water Department	Pennsylvania	Philadelphia	1,600,000	Community	Surface water
11	City of Baltimore	Maryland	Baltimore city	1,600,000	Community	Surface water
12	Las Vegas Valley Water District	Nevada	Clark	1,539,277	Community	Purchased surface water
13	East Bay MUD	California	Alameda	1,442,800	Community	Surface water
14	San Diego, City of	California	San Diego	1,385,379	Community	Surface water
15	Dallas Water Utility	Texas	Dallas	1,356,479	Community	Surface water