California utilities with very hard water.

Above 180 mg/L (10.5 grains per gallon). 718 utilities serving 5.6 million people as they report it, largest first.

1 to 100 of 718, by people served

California utilities with very hard water, 1 to 100
Utility	Based in	Serves	Hardness, mg/L	Grains per gallon
Irvine Ranch Water District	Irvine	450,323	214 to 293	12.5 to 17.1
City of Anaheim	Anaheim	350,254	318	18.6
Glendale - City, Water Dept.	Glendale	192,212	370	21.6
Sweetwater Authority	Chula Vista	184,915	193	11.3
City of Garden Grove	Garden Grove	174,226	331	19.4
City of Sunnyvale	Sunnyvale	157,566	280	16.4
City of Fullerton	Fullerton	140,054	212	12.4
Great Oaks WC Inc	San Jose	112,582	305	17.8
Ventura Water Department	Ventura	112,285	517	30.2
City of Santa Maria Utilities Department	Santa Maria	112,208	500	29.2
San Bernardino Valley WD	San Bernardino	109,608	248	14.5
Burbank - City, Water Dept.	Burbank	106,146	330	19.3
California Water Service Co. - Herm/Redo	San Jose	100,072	415	24.3
City of San Jose - Evg/Edv/Coy	San Jose	99,783	320	18.7
Ventura Wwd No. 8 - Simi Valley	Simi Valley	94,736	527	30.8
Olivenhain MWD	Encinitas	86,458	227	13.3
Goleta Water District	Goleta	85,535	485	28.4
Yorba Linda Water District	Placentia	84,292	344	20.1
City of Mountain View	Mountain View	81,340	269	15.7
City of Pleasanton	Pleasanton	76,689	343	20.1
Liberty Utilities - Bellflower - Norwalk	Downey	72,472	290	17
Lynwood - City, Water Dept.	Lynwood	66,967	270	15.8
Suburban Water Systems - Whittier	Covina	66,565	243	14.2
City of Watsonville	Watsonville	65,231	230	13.5
Brentwood	Brentwood	64,513	369	21.6
Gswc - Florence/Graham	Anaheim	63,472	350	20.5
California Water Service - S San Francisco	San Jose	62,609	382	22.3
City of la Habra	La Habra	61,202	298	17.4
Gswc - San Dimas	San Dimas	56,564	299	17.5
Gswc - Bell, Bell Gardens	Anaheim	55,050	221	12.9
City of San Clemente	San Clemente	51,545	219	12.8
Whittier - City, Water Dept.	Whittier	49,954	265	15.5
City of Poway	Poway	49,888	224	13.1
City of Los Banos	Los Banos	48,896	275	16.1
City of San Jose - Nsj/Alviso	San Jose	48,082	278	16.3
City of Morgan Hill	Morgan Hill	47,374	247	14.4
Bellflower - Somerset MWC	Bellflower	46,300	272	15.9
Golden State Water Company - Simi Valley	Rancho Cordova	45,086	855	50
City of El Centro	El Centro	44,124	315	18.4
Gswc - Norwalk	Anaheim	43,167	398	23.3
South Coast Water District	Laguna Beach	41,194	750	43.9
Lompoc - City Water Utility Div	Lompoc	40,538	574	33.5
City of Calexico	Calexico	40,357	330	19.3
Rubidoux Community SD	Jurupa Valley	38,522	268	15.6
Antelope Valley E Kern WTR Agy - Rosamond	Palmdale	37,634	205	12
Ventura Cwwd No. 1 - Moorpark	Moorpark	35,514	255	14.9
Lakeside WD	Lakeside	35,500	500	29.2
Golden State Water Company - Orcutt	Santa Maria	34,267	380	22.2
Manhattan Beach - City, Water Dept.	Manhattan Beach	34,051	381	22.3
Atascadero Mutual Water Co	Atascadero	33,307	310	18.1
Camrosa Water District	Camarillo	32,700	434	25.4
City of Santa Paula	Santa Paula	31,786	539	31.5
City of East Palo Alto	East Palo Alto	29,519	209	12.2
Vernon - City, Water Dept.	Vernon	28,112	225	13.2
City of Brawley	Brawley	26,862	330	19.3
Montebello Land & Water Co.	Montebello	26,554	205	12
Sunnyslope County Water Dist	Hollister	25,486	401	23.5
City of Patterson	Patterson	24,977	400	23.4
Stanford University	Stanford	23,817	395	23.1
San Fernando - City, Water Dept.	San Fernando	23,364	268	15.7
El Monte - City, Water Dept.	El Monte	23,000	252	14.7
City of Imperial	Imperial	22,102	320	18.7
Santa Fe I.D.	Rancho Santa Fe	21,539	350	20.5
Cal/Am Water Company - Baldwin Hills	Rosemead	20,724	269	15.7
Lomita - City, Water Dept.	Lomita	20,256	340	19.9
City of Soledad	Soledad	19,732	260	15.2
City of Greenfield	Greenfield	18,967	282	16.5
Fillmore Water Dept	Fillmore	16,419	438	25.6
Carpinteria Valley Water District	Carpinteria	16,356	373	21.8
City of Cupertino	Cupertino	16,336	337	19.7
Walnut Park Mutual Water Co.	Huntington Park	16,180	205	12
Huntington Park - City, Water Dept.	Huntington Park	15,437	220	12.9
California Mens Colony	San Luis Obispo	15,000	339	19.8
American Water O&M, LLC - Vsfb	Vandenberg Sfb	14,971	250	14.6
Cwsc King City	San Jose	14,046	200	11.7
Tract 180 Mutual Water Co.	Cudahy	14,000	222	13
Nipomo Comm Services Dist	Nipomo	13,771	294	17.2
Trabuco Canyon Water District	Trabuco Canyon	13,659	287	16.8
Muscoy MWC No. 1	San Bernardino	13,000	225	13.2
City of Grover Beach Public Works Dept	Grover Beach	12,701	210	12.3
City of Newman - Water Department	Newman	12,389	390	22.8
Montecito Water Dist	Santa Barbara	12,010	365	21.3
Casitas Municipal Water Dist	Oak View	11,005	277	16.2
Gswc - Willowbrook	Anaheim	10,793	241	14.1
Valley Water Co.	La Canada Flintridge	10,113	399	23.3
City of Blythe -	Blythe	9,735	550	32.2
La Canada Irrigation Dist.	La Canada	9,258	265	15.5
Guadalupe Water Department	Guadalupe	8,897	405	23.7
Lincoln Avenue Water Co.	Altadena	8,721	219	12.8
Tract 349 Mutual Water Co.	Cudahy	8,700	220	12.9
La Puente Valley CWD	La Puente	8,276	221	12.9
Gswc - Hollydale	Anaheim	8,099	268	15.6
Pismo Beach Water Department	Pismo Beach	7,944	490	28.6
Valencia Heights Water Co.	West Covina	7,775	540	31.6
Cwsc Salinas Hills	San Jose	7,733	290	17
Oceano Comm Services Dist.	Oceano	7,598	523	30.6
Gswc - Calipatria	San Dimas	7,475	350	20.5
Heber Public Utility District	Heber	7,312	340	19.9
Vandenberg Village Comm. Serv. Dist.	Lompoc	7,308	395	23.1
Golden State WC - Cowan Heights	Anaheim	7,006	246	14.4

Source: California State Water Resources Control Board, Division of Drinking Water, 2,449 utilities, results from Jan. 2, 2019 to July 14, 2026, read Oct. 10, 2026. Each sampling point is taken at its median; a figure is typical where every point falls in one band.

Also: 7 utilities’ own water quality reports, read by hand, each named on the utility’s page.

Bands are the U.S. Geological Survey’s, at 17.1 mg/L to the grain. People served is what each utility reports; where one sells water to another, the same people can be counted twice. How hardness is measured here.

1 to 100 of 718, by people served

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