Los Angeles County, California — public water systems

At a glance

275 active public water systems are filed under Los Angeles County, California in EPA's SDWIS records, together reporting 10,109,668 people served. The largest is Los Angeles-City, Dept. of Water & Power, which reports serving 3,875,566 people. 198 are community water systems serving people where they live; the other 77 are non-community systems, such as schools, workplaces, campgrounds and gas stations with their own supply.

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

Active systems

275

Population served

10.1M

Community systems

198

Groundwater share

59.3%

How does Los Angeles County compare with other California counties?

Los Angeles County has the 7th-most active public water systems among the 201 counties listed for active California systems in EPA records; among the 72 with 3 or more systems, the median has 73. Its systems report 10,109,668 people served in total, the largest county figure in the state and 24% of the statewide total. The average system here reports serving 36,762 people, about 6.4 times the California average of 5,706. Population figures are what each system reports; people served by more than one system, such as a wholesaler and the town that buys from it, are counted by each.

Where does Los Angeles County's drinking water come from?

By primary water source, Los Angeles County's active systems draw on groundwater (156, 57%), purchased surface water (90, 33%), surface water (22, 8%) and groundwater under influence of surface water (4, 1.5%). Overall, 59% rely mainly on groundwater (including purchased groundwater) and 41% on surface water, compared with 85% and 15% across California. Groundwater means the system draws its water from wells or springs fed by underground aquifers. The county's largest system, Los Angeles-City, Dept. of Water & Power, draws primarily on surface water.

What kinds of water systems operate in Los Angeles County?

Los Angeles County's active systems break down as 198 community systems (72%), 23 non-transient non-community systems (8.4%) and 54 transient non-community systems (20%). A community water system serves at least 15 connections used by year-round residents, or regularly serves at least 25 year-round residents. Homes, apartments and mobile-home parks are served by these. A non-transient non-community water system regularly serves at least 25 of the same people for more than six months a year, but not where they live. Schools, factories, office buildings and hospitals with their own supply are typical examples. A transient non-community water system serves places where people do not stay long, such as gas stations and campgrounds, and regularly serves at least 25 people a day for at least 60 days a year. EPA lists their owner types as private (55%), local government (36%), federal government (6.9%) and state government (2.2%).

The 50 largest water systems in Los Angeles County

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Active public water systems in Los Angeles County, California
#	Water system	County	Population served	Type	Source
1	Los Angeles-City, Dept. of Water & Power	Los Angeles	3,875,566	Community	Surface water
2	Long Beach Utilities Department	Los Angeles	466,772	Community	Purchased surface water
3	Santa Clarita Valley Water Agency	Los Angeles	294,090	Community	Surface water
4	Gswc - Southwest	Los Angeles	277,740	Community	Purchased surface water
5	San Gabriel Valley Water Co.-El Monte	Los Angeles	248,000	Community	Groundwater
6	Los Angeles Cwwd 40 Reg 4 & 34 Lancaster	Los Angeles	208,129	Community	Purchased surface water
7	Glendale-City, Water Dept.	Los Angeles	188,784	Community	Purchased surface water
8	Suburban Water Systems-San Jose	Los Angeles	168,843	Community	Purchased surface water
9	Pasadena Water and Power	Los Angeles	164,344	Community	Purchased surface water
10	California Water Service Co. - Ela	Los Angeles	152,474	Community	Purchased surface water
11	Pomona - City, Water Dept.	Los Angeles	151,713	Community	Surface water
12	California Water Service Co. - Dominguez	Los Angeles	143,996	Community	Purchased surface water
13	Palmdale Water Dist.	Los Angeles	126,804	Community	Surface water
14	Downey - City, Water Dept.	Los Angeles	110,556	Community	Groundwater
15	Azusa Light and Water	Los Angeles	110,044	Community	Surface water
16	Torrance-City, Water Dept.	Los Angeles	106,183	Community	Purchased surface water
17	Burbank-City, Water Dept.	Los Angeles	105,603	Community	Purchased surface water
18	Walnut Valley Water District	Los Angeles	100,941	Community	Purchased surface water
19	California Water Service Co. - Herm/Redo	Los Angeles	96,853	Community	Purchased surface water
20	Santa Monica-City, Water Division	Los Angeles	89,947	Community	Purchased surface water
21	Inglewood- City, Water Dept.	Los Angeles	80,824	Community	Purchased surface water
22	City of Alhambra	Los Angeles	79,776	Community	Purchased surface water
23	South Gate-City, Water Dept.	Los Angeles	76,443	Community	Purchased surface water
24	Compton-City, Water Dept.	Los Angeles	74,877	Community	Purchased surface water
25	Liberty Utilities - Bellflower-Norwalk	Los Angeles	72,624	Community	Purchased surface water
26	Las Virgenes Mwd	Los Angeles	72,602	Community	Surface water
27	California Water Service Co. - Palos Ver	Los Angeles	71,452	Community	Purchased surface water
28	Valley County Water Dist.	Los Angeles	68,871	Community	Groundwater
29	Lynwood-City, Water Dept.	Los Angeles	66,967	Community	Purchased surface water
30	Lakewood - City, Water Dept.	Los Angeles	66,135	Community	Groundwater
31	Suburban Water Systems-Whittier	Los Angeles	66,045	Community	Groundwater
32	Gswc - Florence/Graham	Los Angeles	63,472	Community	Purchased surface water
33	Monterey Park-City, Water Dept.	Los Angeles	62,183	Community	Groundwater
34	Suburban Water Systems-La Mirada	Los Angeles	56,793	Community	Purchased surface water
35	Gswc-San Dimas	Los Angeles	56,538	Community	Purchased surface water
36	Rowland Water District	Los Angeles	56,100	Community	Purchased surface water
37	Paramount - City, Water Dept.	Los Angeles	55,200	Community	Purchased surface water
38	Gswc - Bell, Bell Gardens	Los Angeles	55,050	Community	Purchased surface water
39	City of Arcadia	Los Angeles	51,361	Community	Groundwater
40	Gswc - Artesia	Los Angeles	50,415	Community	Groundwater
41	Whittier-City, Water Dept.	Los Angeles	49,954	Community	Groundwater
42	Glendora-City, Water Dept.	Los Angeles	49,934	Community	Purchased surface water
43	Cal/Am Water Company - San Marino	Los Angeles	47,995	Community	Purchased surface water
44	Cerritos - City, Water Dept.	Los Angeles	47,475	Community	Purchased surface water
45	Bellflower - Somerset Mwc	Los Angeles	46,300	Community	Purchased surface water
46	Hawthorne-City Water Dept.	Los Angeles	44,718	Community	Purchased surface water
47	Gswc - Norwalk	Los Angeles	43,167	Community	Purchased surface water
48	Pico Rivera - City, Water Dept.	Los Angeles	40,600	Community	Groundwater
49	Beverly Hills-City, Water Dept.	Los Angeles	40,121	Community	Purchased surface water
50	Gswc - Claremont	Los Angeles	39,730	Community	Purchased surface water

All other water systems in Los Angeles County (219)

The remaining active systems filed under Los Angeles County, largest first, with the population each reports serving.

Los Angeles County water systems: frequently asked questions

How many public water systems are in Los Angeles County, California?

EPA's SDWIS records file 275 active public water systems under Los Angeles County, California: 198 community systems (72%), 23 non-transient non-community systems (8.4%) and 54 transient non-community systems (20%).

Who supplies drinking water in Los Angeles County, CA?

The largest community water systems filed under Los Angeles County are Los Angeles-City, Dept. of Water & Power (3,875,566 people served), Long Beach Utilities Department (466,772 people served) and Santa Clarita Valley Water Agency (294,090 people served). Which system serves a particular address depends on its service area, which EPA's SDWIS records do not include; a water bill or the local utility can confirm it.

Does Los Angeles County's drinking water come from groundwater or surface water?

Of the 275 active public water systems in Los Angeles County, 59% draw mainly on groundwater and 41% on surface water, counting purchased supplies. The largest system, Los Angeles-City, Dept. of Water & Power, uses surface water.

Where can I find a water quality report for Los Angeles County?

Each community water system must deliver an annual water quality report, called a Consumer Confidence Report, to its customers by July 1, covering the previous calendar year. 198 community systems are filed under Los Angeles County, so the report to look for is the one from the system that supplies your address.

How can I check violations for a water system in Los Angeles County?

Open the system's profile from the list on this page. Each profile shows the most recent Safe Drinking Water Act violations in EPA's records, with plain-English labels and whether each one is resolved. For current compliance status, EPA ECHO is the primary source.

More California water systems

About this data

Source: U.S. EPA Safe Drinking Water Information System (SDWIS) and SDWA violation records, via EPA ECHO, as published October 1, 2026 — AquaCensus refreshes it quarterly. See the methodology for how records are matched, cleaned and scored.

Cite as: AquaCensus, “Public water systems in Los Angeles County, California”, https://aquacensus.com/water-systems/california/los-angeles (data as of October 1, 2026).