California Water Systems

Compiled by PlainEnviro Editorial, Environmental Data Editorial Team · July 13, 2026

3,077 community water systems in California, ranked by violation count. Data from EPA Safe Drinking Water Information System (SDWIS).

Water Systems

3,077

Total Violations

17,550

Health Violations

1,274 systems

Population Served

40,363,187

California operates 3,077 community water systems regulated by the EPA Safe Drinking Water Information System (SDWIS) under the Safe Drinking Water Act. Together these utilities serve an estimated 40,363,187 residents, each filing compliance results with the state's primacy agency and, for federally listed contaminants, with the U.S. Environmental Protection Agency.

Across the state, SDWIS records contain 17,550 total violations, of which 1274 systems carry at least one active health-based violation, a Maximum Contaminant Level (MCL) exceedance or treatment-technique failure. That represents roughly 41% of California systems.

Violation counts reflect both infrastructure realities and reporting diligence, a state with more small rural systems will accumulate more monitoring-type violations without necessarily delivering worse water. Health-based violations are the stronger safety signal. A past violation does not itself indicate current unsafe water; utilities must notify customers, remediate, and publish an annual Consumer Confidence Report. All numbers below draw directly from the federal SDWIS record.

Which water systems have violations? (125)

#	System Name	City	Source	Violations	Pop. Served	Health
1	US ARMY FORT IRWIN Fort Irwin	Fort Irwin	Groundwater	180	15,701	Yes
2	LINDSAY, CITY OF Linsday	Linsday	Surface Water	173	12,659	Yes
3	ARVIN COMMUNITY SERVICES DIST Arvin	Arvin	Groundwater	133	19,669	Yes
4	LEMOORE, CITY OF Lemoore	Lemoore	Groundwater	119	27,185	Yes
5	GREENFIELD COUNTY WD Bakersfield	Bakersfield	Groundwater	74	11,590	Yes
6	LEMOORE NAVAL AIR STATION Lemoore	Lemoore	Surface Water	62	15,000	Yes
7	Pala North Pala	Pala	Groundwater	44	14,280	Yes
8	SUISUN-SOLANO WATER AUTHORITY Vacaville	Vacaville	Surface Water	41	29,105	Yes
9	LAMONT PUBLIC UTILITY DIST Lamont	Lamont	Groundwater	39	19,057	Yes
10	AVENAL, CITY OF Avenal	Avenal	Surface Water	38	13,696	Yes
11	HURON, CITY OF Huron	Huron	Surface Water	34	9,306	Yes
12	KINGSBURG, CITY OF Kingsburg	Kingsburg	Groundwater	33	13,540	Yes
13	INDIAN HILLS CAMP Jamul	Jamul	Groundwater	32	13,032	Yes
14	IMPERIAL, CITY OF Imperial	Imperial	Surface Water	29	21,591	Yes
15	MCFARLAND, CITY OF Mcfarland	Mcfarland	Groundwater	28	14,161	Yes
16	Table Mountain Rancheria Friant	Friant	Surface Water	24	10,675	Yes
17	CITY OF YUBA CITY Yuba City	Yuba City	Surface Water	20	70,256	Yes
18	OILDALE MWC Bakersfield	Bakersfield	Surface Water	19	44,899	Yes
19	CITY OF STOCKTON Stockton	Stockton	Surface Water	18	191,302	Yes
20	HANFORD, CITY OF Hanford	Hanford	Groundwater	18	62,127	Yes
21	AMERICAN CANYON, CITY OF American Canyon	American Canyon	Surface Water	18	21,437	Yes
22	HOLLISTER, CITY OF Hollister	Hollister	Surface Water	17	26,017	Yes
23	CAMP PENDLETON (SOUTH) Camp Pendleton	Camp Pendleton	Groundwater	16	42,219	Yes
24	COALINGA-CITY Coalinga	Coalinga	Surface Water	14	17,277	Yes
25	CITY OF LIVINGSTON Livingston	Livingston	Groundwater	13	14,894	Yes
26	EAST VALLEY WATER DISTRICT Highland	Highland	Surface Water	12	108,629	Yes
27	TEJON CASTAC WD - I5 & LAVAL RD Lebec	Lebec	Surface Water	12	38,125	Yes
28	WASCO, CITY OF Wasco	Wasco	Groundwater	12	22,757	Yes
29	YUCAIPA VALLEY WATER DISTRICT Yucaipa	Yucaipa	Surface Water	11	52,010	Yes
30	SIGNAL HILL - CITY, WATER DEPT. Signal Hill	Signal Hill	Surface Water	11	11,848	Yes
31	CUYAMACA WATER DISTRICT Julian	Julian	Groundwater	10	33,030	Yes
32	CCWD - EBBETTS PASS San Andreas	San Andreas	Surface Water	10	11,545	Yes
33	PISMO BEACH WATER DEPARTMENT Pismo Beach	Pismo Beach	Surface Water	10	8,036	Yes
34	GALT, CITY OF Galt	Galt	Groundwater	9	26,536	Yes
35	LOS ANGELES-CITY, DEPT. OF WATER & POWER Los Angeles	Los Angeles	Surface Water	8	3,875,566	Yes
36	CALIF STATE POLYTECHNICAL UNIV - POMONA Pomona	Pomona	Surface Water	8	29,854	Yes
37	CALIFORNIA INSTITUTION FOR MEN Chino	Chino	Groundwater	8	10,667	Yes
38	SAN GABRIEL VALLEY WATER CO.-EL MONTE El Monte	El Monte	Groundwater	6	248,000	Yes
39	CITY OF SUNNYVALE Sunnyvale	Sunnyvale	Surface Water	6	157,566	Yes
40	FLORIN COUNTY WATER DISTRICT Sacramento	Sacramento	Groundwater	6	7,831	Yes
41	CITY OF NEWMAN-WATER DEPARTMENT Newman	Newman	Groundwater	5	12,207	Yes
42	WINTON WATER & SANITARY DIST Winton	Winton	Groundwater	5	9,745	Yes
43	CITY OF ORANGE COVE Orange Cove	Orange Cove	Surface Water	5	9,525	Yes
44	SAN JOSE WATER San Jose	San Jose	Surface Water	4	1,039,920	Yes
45	CITY OF VALLEJO Vallejo	Vallejo	Surface Water	4	121,420	Yes
46	CAL-WATER SERVICE CO.-CHICO San Jose	San Jose	Groundwater	4	114,925	Yes
47	DOWNEY - CITY, WATER DEPT. Downey	Downey	Groundwater	4	108,816	Yes
48	CITY OF MOUNTAIN VIEW Mountain View	Mountain View	Surface Water	4	81,501	Yes
49	CERES, CITY OF Ceres	Ceres	Surface Water	4	54,513	Yes
50	GOLDEN STATE WATER CO. - CORDOVA Rancho Cordova	Rancho Cordova	Surface Water	4	47,161	Yes
51	GOLDEN STATE WATER CO - BARSTOW Apple Valley	Apple Valley	Groundwater	4	32,547	Yes
52	EAST NILES CSD Bakersfield	Bakersfield	Surface Water	4	32,517	Yes
53	CORCORAN, CITY OF Corcoran	Corcoran	Groundwater	4	22,808	Yes
54	SHAFTER, CITY OF Shafter	Shafter	Groundwater	4	21,915	Yes
55	USMC - 29 PALMS 29 Palms	29 Palms	Groundwater	4	15,248	Yes
56	CAMP PENDLETON (NORTH) Camp Pendleton	Camp Pendleton	Groundwater	4	12,651	Yes
57	CASITAS MUNICIPAL WATER DIST Oak View	Oak View	Surface Water	4	11,005	Yes
58	BLYTHE - CITY OF Blythe	Blythe	Groundwater	4	9,798	Yes
59	FIREBAUGH CITY Firebaugh	Firebaugh	Groundwater	4	8,096	Yes
60	EL DORADO ID - MAIN Placerville	Placerville	Surface Water	3	132,171	Yes
61	TRACY, CITY OF Tracy	Tracy	Surface Water	3	96,609	Yes
62	CITY OF REDWOOD CITY Redwood City	Redwood City	Surface Water	3	92,819	Yes
63	NAPA, CITY OF Napa	Napa	Surface Water	3	84,804	Yes
64	TURLOCK, CITY OF Turlock	Turlock	Surface Water	3	72,682	Yes
65	CITY OF PALO ALTO Palo Alto	Palo Alto	Surface Water	3	67,231	Yes
66	CALIFORNIA WATER SERVICE-S SAN FRANCISCO San Jose	San Jose	Surface Water	3	64,146	Yes
67	CITY OF GILROY Gilroy	Gilroy	Groundwater	3	59,203	Yes
68	STANFORD UNIVERSITY Stanford	Stanford	Surface Water	3	35,853	Yes
69	CALIFORNIA WATER SERVICE - SAN CARLOS San Jose	San Jose	Surface Water	3	35,344	Yes
70	RIVERBANK, CITY OF Riverbank	Riverbank	Groundwater	3	24,834	Yes
71	NASA AMES RESEARCH CENTER Moffett Field	Moffett Field	Surface Water	3	16,273	Yes
72	RIO LINDA/ELVERTA COMMUNITY WATER DIST Rio Linda	Rio Linda	Groundwater	3	15,460	Yes
73	MENDOTA, CITY OF Mendota	Mendota	Groundwater	3	11,404	Yes
74	EDWARDS AFB - MAIN BASE Edwards Afb	Edwards Afb	Surface Water	3	11,316	Yes
75	CITY OF FULLERTON Fullerton	Fullerton	Surface Water	2	139,461	Yes
76	VICTORVILLE WATER DISTRICT Victorville	Victorville	Surface Water	2	135,983	Yes
77	VENTURA WATER DEPARTMENT Ventura	Ventura	Surface Water	2	113,500	Yes
78	CAL-AM WATER CORONADO Imperial Beach	Imperial Beach	Surface Water	2	106,000	Yes
79	CALIFORNIA WATER SERVICE - SAN MATEO San Jose	San Jose	Surface Water	2	102,348	Yes
80	CWSC LOS ALTOS SUBURBAN San Jose	San Jose	Surface Water	2	69,973	Yes
81	BRENTWOOD Brentwood	Brentwood	Surface Water	2	64,513	Yes
82	CALIFORNIA WATER SERVICE - BEAR GULCH San Jose	San Jose	Surface Water	2	61,431	Yes
83	LAKE HEMET MWD Hemet	Hemet	Groundwater	2	52,913	Yes
84	UC - DAVIS Davis	Davis	Surface Water	2	49,616	Yes
85	CALEXICO, CITY OF Calexico	Calexico	Surface Water	2	40,357	Yes
86	LA VERNE, CITY WD La Verne	La Verne	Surface Water	2	31,334	Yes
87	MID-PENINSULA WATER DISTRICT Belmont	Belmont	Surface Water	2	30,609	Yes
88	MENLO PARK MUNICIPAL WATER Menlo Park	Menlo Park	Surface Water	2	22,362	Yes
89	SAN LORENZO VALLEY WATER DIST Boulder Creek	Boulder Creek	Surface Water	2	21,145	Yes
90	CALIFORNIA WATER SERVICE CO.-TRAVIS AFB San Jose	San Jose	Surface Water	2	18,111	Yes
91	CITY OF RED BLUFF Red Bluff	Red Bluff	Groundwater	2	14,710	Yes
92	CALIFORNIA CITY, CITY OF California City	California City	Surface Water	2	14,198	Yes
93	THERMALITO WATER & SEWER DIST Oroville	Oroville	Surface Water	2	12,136	Yes
94	EXETER, CITY OF Exeter	Exeter	Groundwater	2	11,169	Yes
95	CLOVERDALE, CITY OF Cloverdale	Cloverdale	Surface Water	2	10,398	Yes
96	MAMMOTH CWD Mammoth Lakes	Mammoth Lakes	Surface Water	2	8,234	Yes
97	WOODLAKE, CITY OF Woodlake	Woodlake	Groundwater	2	7,846	Yes
98	SCWA - LAGUNA/VINEYARD Sacramento	Sacramento	Surface Water	1	184,896	Yes
99	CITY OF FAIRFIELD Fairfield	Fairfield	Surface Water	1	120,377	Yes
100	PORTERVILLE, CITY OF Porterville	Porterville	Groundwater	1	63,164	Yes
101	MONTEREY PARK-CITY, WATER DEPT. Los Angeles	Los Angeles	Groundwater	1	62,183	Yes
102	CITY OF WEST SACRAMENTO West Sacramento	West Sacramento	Surface Water	1	53,355	Yes
103	CITY OF LOS BANOS Los Banos	Los Banos	Groundwater	1	47,419	Yes
104	SCWA MATHER-SUNRISE Sacramento	Sacramento	Surface Water	1	30,825	Yes
105	CITY OF EAST PALO ALTO East Palo Alto	East Palo Alto	Surface Water	1	29,519	Yes
106	CITY OF SANGER Sanger	Sanger	Groundwater	1	26,357	Yes
107	OAKDALE, CITY OF Oakdale	Oakdale	Groundwater	1	23,235	Yes
108	LOMITA-CITY, WATER DEPT. Lomita	Lomita	Surface Water	1	20,256	Yes
109	TWENTYNINE PALMS WATER DISTRICT Twentynine Palms	Twentynine Palms	Groundwater	1	18,795	Yes
110	BAKMAN WATER COMPANY Fresno	Fresno	Groundwater	1	17,393	Yes
111	CALIFORNIA MENS COLONY San Luis Obispo	San Luis Obispo	Surface Water	1	15,000	Yes
112	AMERICAN WATER O&M, LLC - VSFB Vandenberg Sfb	Vandenberg Sfb	Surface Water	1	14,971	Yes
113	CITY OF PARLIER Parlier	Parlier	Groundwater	1	14,576	Yes
114	TRABUCO CANYON WATER DISTRICT Trabuco Canyon	Trabuco Canyon	Surface Water	1	13,659	Yes
115	MUSCOY MWC NO. 1 San Bernardino	San Bernardino	Groundwater	1	13,000	Yes
116	CITY OF ANDERSON Anderson	Anderson	Groundwater	1	11,147	Yes
117	SONOMA STATE UNIVERSITY Rohnert Park	Rohnert Park	Groundwater	1	10,986	Yes
118	FARMERSVILLE, CITY OF Farmersville	Farmersville	Groundwater	1	10,243	Yes
119	SCWA - ARDEN PARK VISTA Sacramento	Sacramento	Groundwater	1	10,101	Yes
120	LAKE HENSHAW RESORT INC. Santa Ysabel	Santa Ysabel	Groundwater	1	9,913	Yes
121	CCWD - JENNY LIND San Andreas	San Andreas	Surface Water	1	9,861	Yes
122	TEHACHAPI, CITY OF Tehachapi	Tehachapi	Groundwater	1	9,094	Yes
123	CLEAR CREEK CSD-ANDERSON Anderson	Anderson	Surface Water	1	8,900	Yes
124	AWA BUCKHORN PLANT Sutter Creek	Sutter Creek	Surface Water	1	8,791	Yes
125	YREKA, CITY OF Yreka	Yreka	Surface Water	1	7,825	Yes

Systems with No Violations (375)

375 water systems in California have zero recorded violations. Showing the 50 largest by population served.

EAST BAY MUD (1,442,800) SAN DIEGO, CITY OF (1,385,379) SFPUC CITY DISTRIBUTION DIVISION (848,019) EASTERN MUNICIPAL WD (666,581) CITY OF FRESNO (545,716) CITY OF SACRAMENTO MAIN (520,407) LONG BEACH UTILITIES DEPARTMENT (466,772) IRVINE RANCH WATER DISTRICT (444,800) CITY OF ANAHEIM (348,593) ALAMEDA COUNTY WATER DISTRICT (344,000) CITY OF SANTA ANA (310,539) RIVERSIDE, CITY OF (298,398) SANTA CLARITA VALLEY WATER AGENCY (294,090) GSWC - SOUTHWEST (277,740) HELIX WATER DISTRICT (277,668) COACHELLA VWD: COVE COMMUNITY (270,000) CWS - BAKERSFIELD (267,881) OTAY WATER DISTRICT (238,008) SAN GABRIEL VALLEY WC - FONTANA (237,700) MODESTO, CITY OF (218,771) SAN BERNARDINO CITY (214,665) CUCAMONGA VALLEY WATER DISTRICT (211,069) LOS ANGELES CWWD 40 REG 4 & 34 LANCASTER (208,129) CITY OF HUNTINGTON BEACH (201,000) OXNARD WATER DEPT (200,232) CONTRA COSTA WATER DISTRICT (198,000) SACRAMENTO SUBURBAN WATER DISTRICT (194,444) SWEETWATER AUTHORITY (191,282) GLENDALE-CITY, WATER DEPT. (188,784) MARIN MUNICIPAL WATER DISTRICT (186,895) ONTARIO MUNICIPAL UTILITIES COMPANY (185,010) CALIFORNIA WATER SERVICE - STOCKTON (176,266) SANTA ROSA, CITY OF (175,396) CITY OF GARDEN GROVE (174,226) OCEANSIDE, CITY OF (171,483) MOULTON NIGUEL WATER DISTRICT (170,236) ELSINORE VALLEY MWD (169,455) SUBURBAN WATER SYSTEMS-SAN JOSE (168,843) CORONA, CITY OF (168,575) SANTA MARGARITA WATER DISTRICT (168,289) PASADENA WATER AND POWER (164,344) CITY OF HAYWARD (162,954) BAKERSFIELD, CITY OF (160,144) CITY OF ROSEVILLE (155,612) CALIFORNIA WATER SERVICE CO. - ELA (152,474) POMONA - CITY, WATER DEPT. (151,713) CWS - VISALIA (148,496) RANCHO CALIFORNIA WATER DISTRICT (146,147) CALIFORNIA WATER SERVICE CO. - DOMINGUEZ (143,996) ESCONDIDO, CITY OF (137,044) +325 more

All Water Systems in California (3,077)

Page 14 of 62, ordered by population served.

System	Population Served	Violations
TESORO VIEJO MASTER MWC, INC.	3,885	0
TREASURE ISLAND	3,864	0
WOODLANDS DEVELOPMENT	3,862	0
CDCR-HIGH DESERT STATE PRISON	3,857	0
ANGELS, CITY OF	3,836	4
GILBERT STREET COMPLEX	3,833	0
SO. CAL. EDISON CO.-SANTA CATALINA	3,822	0
BISHOP, CITY OF	3,819	4
SAN JOAQUIN COUNTY-MOKELUMNE ACRES	3,802	0
WILLOW COUNTY WATER DISTRICT	3,797	0
FORESTVILLE WATER DISTRICT	3,788	0
AMERICAN VALLEY CSD	3,778	6
IDYLLWILD WATER DISTRICT	3,762	4
CAL AM - OAKHURST	3,693	368
MT. SHASTA, CITY OF	3,642	11
BROOKTRAILS TOWNSHIP CSD	3,632	0
MISSION HILLS CSD	3,600	0
ESPARTO C.S.D.	3,574	3
LOCKEFORD COMMUNITY SERV. DIST.	3,572	0
CDCR - SIERRA CONSERVATION CENTER	3,571	8
JACKSON VALLEY IRRIGATION DISTRICT	3,553	0
COBB AREA COUNTY WATER DISTRICT	3,515	1
Hoopa Valley-Wide System	3,500	0
PRESIDIO OF SAN FRANCISCO	3,500	0
Colusa Southern System	3,474	0
EAST ORANGE COUNTY WD - RZ	3,464	0
BORREGO WD	3,429	0
CITY OF BRISBANE	3,402	3
GROVELAND COMMUNITY SERV DIST	3,400	3
BOX SPRINGS MUTUAL WC	3,382	0
TAHOE CITY PUD - TAHOE SWISS VILLAGE	3,363	2
RIO ALTO WATER DISTRICT	3,329	0
FOLSOM, CITY OF - ASHLAND	3,317	0
COTTONWOOD WATER DISTRICT	3,316	2
RIO DELL, CITY OF	3,300	0
LUKINS BROTHERS WATER COMPANY	3,277	4
RINCON DEL DIABLO MWD (ID-A)	3,275	0
LAKE DON PEDRO CSD	3,240	1
Arizona Village	3,211	8
VALLEY STATE PRISON	3,173	16
MADERA CO MD10A-MADERA RANCHOS	3,172	0
CWSC OAK HILLS	3,161	0
BURNEY WATER DISTRICT	3,154	1
PLACER CWA - COLFAX	3,149	0
CITY OF NEVADA CITY	3,148	3
AMARILLO MUTUAL WATER COMPANY	3,134	0
SAN ANTONIO WATER COMPANY	3,111	2
HOME GARDENS COUNTY WD	3,095	0
SHASTA C.S.D.	3,069	0
MARYGOLD MWC	3,055	1

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Frequently Asked Questions

How many water systems are in California?

California has 3,077 community water systems tracked by the EPA, serving a combined population of 40,363,187 people.

How many water systems in California have health violations?

1274 water systems in California have health-based violations, which include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations. These represent 41% of all systems in the state.

What is the total number of water violations in California?

California water systems have accumulated 17,550 total violations across all 3,077 community water systems.

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About This Data

Water system data is from the EPA Safe Drinking Water Information System (SDWIS). Health-based violations include Maximum Contaminant Level (MCL) and Treatment Technique (TT) violations that may pose a direct risk to public health. Only community water systems (CWS) are included.

Source: U.S. Environmental Protection Agency, SDWIS Federal Reporting Services U.S. Environmental Protection Agency, SDWIS Federal Reporting Services

Read our methodology - how this data is sourced, computed, and verified.

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