How many public water systems are in District of Columbia?

District of Columbia has 12 active public water systems in EPA SDWIS records, including 4 community water systems. Together they report serving 697.4K people.

What is the largest water system in District of Columbia?

D.C. Water and Sewer Authority is the largest active public water system in District of Columbia, serving a reported 632,323 people.

Does District of Columbia rely more on groundwater or surface water?

50% of District of Columbia's active public water systems draw primarily on groundwater and 50% on surface water (including purchased supplies).

District of Columbia public water systems

12 active systems regulated under the Safe Drinking Water Act, serving a reported 697.4K people across 8 counties.

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

Active systems

Population served

697.4K

Community systems

Groundwater share

50%

System types in District of Columbia

Community water system

Non-transient non-community water system

Transient non-community water system

Largest water systems in District of Columbia

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The largest active public water systems in District of Columbia by population served
#	Water system	County	Population served	Type	Source
1	D.C. Water and Sewer Authority	District of Columbia	632,323	Community	Purchased surface water
2	National Airport	Arlington	28,055	Non-transient non-community	Purchased surface water
3	Joint Base Anacostia - Bolling	District of Columbia	19,312	Community	Purchased surface water
4	Naval Station Washington - Wny	District of Columbia	16,800	Community	Purchased surface water
5	Naval Observatory	District of Columbia	250	Non-transient non-community	Purchased surface water
6	Navcc-Library of Congress Packard Campus	Culpeper	200	Non-transient non-community	Groundwater
7	Raven Rock Mountain Complex	Adams	150	Non-transient non-community	Groundwater
8	Huspp 180 First Ave	Lackawanna	100	Non-transient non-community	Groundwater
9	Kent Island Shopping Center	Queen Anne's	88	Non-transient non-community	Groundwater
10	Jemals Bay 50 Plaza	Anne Arundel	50	Non-transient non-community	Groundwater
11	Camp Brighton Woods (Girl Scouts Nation)	Montgomery	30	Transient non-community	Groundwater

By county

District of Columbia5 systems

Anne Arundel1 systems

Montgomery1 systems

Queen Anne's1 systems

Lackawanna1 systems

Adams1 systems

Arlington1 systems

Culpeper1 systems