Water Quality in California
2,819 water systems • 818 cities • EPA SDWIS Data
2,819
Water Systems
39,276
Total Violations
18,881
Health-Based Violations
40,093,669
Population Served
Overview
California has 2,819 active community water systems serving 40,093,669 people. These systems have accumulated 39,276 EPA Safe Drinking Water Act violations on record, of which 18,881 are health-based violations (meaning a contaminant exceeded safe levels).
Common contaminants found in violations: E. coli, Stage 2 DBP, Fecal Coliform, Total Haloacetic Acids (HAA5), Disinfection Byproducts, TTHM, Contaminant 2920, Gross Alpha, Mercury, Selenium.
Cities with Most Violations in California
| # | City | Violations | Health-Based | Water Systems | Population |
|---|---|---|---|---|---|
| 1 | Rohnert Park | 1,157 | 3 | 6 | 54,984 |
| 2 | Sacramento | 1,022 | 869 | 71 | 1,219,532 |
| 3 | Bakersfield | 923 | 632 | 50 | 137,162 |
| 4 | Fresno | 903 | 484 | 42 | 630,234 |
| 5 | Madera | 818 | 470 | 29 | 85,851 |
| 6 | Chico | 639 | 378 | 30 | 23,374 |
| 7 | Lancaster | 608 | 285 | 19 | 8,296 |
| 8 | Coalinga | 599 | 570 | 6 | 18,440 |
| 9 | Salinas | 567 | 439 | 56 | 64,442 |
| 10 | San Bernardino | 544 | 470 | 12 | 377,910 |
Largest Cities in California
| # | City | Population | Violations | Water Systems |
|---|---|---|---|---|
| 1 | Los Angeles | 4,029,090 | 130 | 16 |
| 2 | San Jose | 3,387,313 | 146 | 65 |
| 3 | Oakland | 1,444,562 | 17 | 5 |
| 4 | San Diego | 1,422,927 | 73 | 5 |
| 5 | Sacramento | 1,219,532 | 1,022 | 71 |
| 6 | Burlingame | 884,627 | 1 | 8 |
| 7 | Anaheim | 789,505 | 15 | 12 |
| 8 | Perris | 666,581 | 0 | 1 |
| 9 | Fresno | 630,234 | 903 | 42 |
| 10 | Long Beach | 466,792 | 105 | 2 |
All Cities in California
| City | Population | Violations | Health Violations | Contaminants |
|---|---|---|---|---|
| Los Angeles | 4,029,090 | 130 | 87 | Barium, Bromate, Chlorine Dioxide +2 more |
| San Jose | 3,387,313 | 146 | 79 | Fecal Coliform, Gross Alpha, Lead +5 more |
| Oakland | 1,444,562 | 17 | 4 | Fecal Coliform |
| San Diego | 1,422,927 | 73 | 16 | E. coli, Fecal Coliform, Stage 2 DBP |
| Sacramento | 1,219,532 | 1,022 | 869 | Barium, Contaminant 1032, E. coli +6 more |
| Burlingame | 884,627 | 1 | 0 | |
| Anaheim | 789,505 | 15 | 2 | Chlorine, Stage 2 DBP |
| Perris | 666,581 | 0 | 0 | |
| Fresno | 630,234 | 903 | 484 | Barium, Chlorine, Contaminant 1094 +11 more |
| Long Beach | 466,792 | 105 | 3 | Selenium, Stage 2 DBP |
| Irvine | 447,634 | 111 | 36 | Arsenic, Selenium, Stage 2 DBP |
| Riverside | 402,159 | 3 | 0 | |
| San Bernardino | 377,910 | 544 | 470 | Barium, Contaminant 4109, Disinfection Byproducts +3 more |
| Alhambra | 357,825 | 0 | 0 | |
| Fremont | 344,145 | 18 | 1 | Stage 2 DBP |
| Covina | 336,030 | 17 | 1 | Chlorine |
| Hawthorne | 321,206 | 8 | 4 | Arsenic |
| Downey | 311,053 | 129 | 28 | E. coli, Gross Alpha |
| Santa Ana | 310,539 | 7 | 0 | |
| Newhall | 294,090 | 0 | 0 | |
| El Monte | 289,546 | 102 | 63 | Barium, Chlorine Dioxide, Nitrate +1 more |
| La Mesa | 277,668 | 0 | 0 | |
| Palm Desert | 274,881 | 41 | 2 | Stage 2 DBP |
| Modesto | 239,487 | 37 | 6 | Haloacetic Acids, Selenium |
| Spring Valley | 239,413 | 24 | 0 | |
| Fontana | 237,700 | 0 | 0 | |
| Rosemead | 225,071 | 48 | 5 | Fecal Coliform, Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Stockton | 223,340 | 443 | 202 | Barium, Chlorine, Contaminant 2920 +8 more |
| Oxnard | 212,540 | 58 | 5 | Selenium, Stage 2 DBP |
| Rancho Cucamonga | 211,546 | 15 | 1 | Contaminant 3001 |
| Rancho Santa Margarita | 207,973 | 10 | 0 | |
| Huntington Beach | 201,976 | 35 | 12 | Disinfection Byproducts, E. coli, Stage 2 DBP |
| Concord | 198,803 | 12 | 1 | Stage 2 DBP |
| Pasadena | 191,916 | 46 | 28 | Selenium |
| Chula Vista | 191,282 | 0 | 0 | |
| Glendale | 188,784 | 0 | 0 | |
| Corte Madera | 186,895 | 0 | 0 | |
| Santa Rosa | 185,941 | 236 | 84 | 1,2-Dichloroethane, Barium, Bromate +5 more |
| Ontario | 185,010 | 0 | 0 | |
| Pomona | 181,567 | 65 | 8 | Stage 2 DBP, TTHM |
| Jurupa Valley | 177,768 | 8 | 0 | |
| Pleasanton | 176,289 | 9 | 1 | Stage 2 DBP |
| Corona | 174,518 | 35 | 4 | Selenium, Stage 2 DBP |
| Garden Grove | 174,226 | 0 | 0 | |
| Escondido | 171,989 | 52 | 28 | Contaminant 4109, Haloacetic Acids, TTHM |
| Oceanside | 171,483 | 0 | 0 | |
| Laguna Hills | 170,959 | 14 | 1 | Stage 2 DBP |
| Lake Elsinore | 169,455 | 0 | 0 | |
| Hayward | 163,080 | 3 | 0 | |
| Rialto | 158,951 | 3 | 0 | |
| Sunnyvale | 157,566 | 228 | 6 | Fecal Coliform |
| San Dimas | 157,316 | 4 | 0 | |
| Roseville | 155,825 | 18 | 2 | Gross Alpha, Stage 2 DBP |
| Temecula | 146,715 | 155 | 2 | Gross Alpha |
| Placerville | 142,442 | 5 | 3 | E. coli, Fecal Coliform |
| Fullerton | 139,580 | 13 | 5 | E. coli, Gross Alpha |
| Bakersfield | 137,162 | 923 | 632 | Barium, Contaminant 2931, Contaminant 2946 +8 more |
| Victorville | 136,159 | 4 | 2 | Gross Alpha |
| Rancho Cordova | 134,193 | 129 | 112 | Barium, Fecal Coliform, Gross Alpha +2 more |
| Vista | 132,430 | 0 | 0 | |
| Clovis | 131,647 | 346 | 238 | Barium, Contaminant 4109, E. coli +5 more |
| Santa Clara | 131,092 | 1 | 0 | |
| Palmdale | 130,538 | 36 | 9 | Barium, Stage 2 DBP, TTHM |
| Encinitas | 126,863 | 4 | 0 | |
| Orange | 124,234 | 3 | 0 | |
| Vallejo | 124,223 | 5 | 5 | Gross Alpha, TTHM |
| Auburn | 123,713 | 3 | 1 | Fecal Coliform |
| Fairfield | 120,468 | 25 | 9 | Selenium, Stage 2 DBP |
| Redding | 119,065 | 88 | 27 | E. coli, Fecal Coliform, Gross Alpha +2 more |
| Santa Barbara | 117,465 | 57 | 11 | Chlorine Dioxide, Disinfection Byproducts, Gross Alpha +1 more |
| Davis | 117,113 | 11 | 2 | Gross Alpha |
| Antioch | 115,074 | 0 | 0 | |
| Ventura | 114,631 | 60 | 28 | Chlorine, E. coli, Stage 2 DBP +2 more |
| San Marcos | 113,596 | 182 | 53 | Lead, Selenium |
| Costa Mesa | 110,450 | 91 | 55 | Contaminant 1028, Contaminant 1032, Fecal Coliform |
| Azusa | 110,159 | 5 | 1 | Stage 2 DBP |
| Santa Maria | 110,059 | 109 | 5 | Selenium |
| Highland | 108,629 | 12 | 12 | TTHM |
| South Lake Tahoe | 107,415 | 50 | 7 | Gross Alpha, Haloacetic Acids, Stage 2 DBP |
| Torrance | 106,183 | 0 | 0 | |
| Imperial Beach | 106,000 | 2 | 2 | E. coli |
| Burbank | 105,603 | 24 | 0 | |
| Daly City | 104,901 | 0 | 0 | |
| Walnut | 100,941 | 0 | 0 | |
| Hesperia | 100,894 | 14 | 1 | Stage 2 DBP |
| Pacific Grove | 98,039 | 5 | 1 | E. coli |
| Tracy | 97,899 | 45 | 12 | Barium, E. coli, Fecal Coliform +2 more |
| Chino | 97,102 | 35 | 8 | Chlorine Dioxide, Gross Alpha, Selenium |
| Elmira | 97,000 | 9 | 0 | |
| Santa Cruz | 96,691 | 55 | 31 | Haloacetic Acids, Selenium, Stage 2 DBP |
| Merced | 96,509 | 14 | 3 | Gross Alpha, Stage 2 DBP |
| Simi Valley | 95,529 | 6 | 0 | |
| Carlsbad | 95,158 | 0 | 0 | |
| Santee | 94,459 | 19 | 8 | Selenium |
| Redwood City | 93,569 | 66 | 11 | E. coli, Fecal Coliform, TTHM +1 more |
| Westminster | 92,216 | 8 | 1 | Chlorine |
| Hemet | 88,540 | 43 | 2 | E. coli |
| Napa | 87,861 | 177 | 71 | Arsenic, E. coli, Gross Alpha +3 more |
| Camarillo | 87,824 | 13 | 0 | |
| Madera | 85,851 | 818 | 470 | Barium, Contaminant 2920, Contaminant 4109 +7 more |
| Folsom | 85,638 | 5 | 0 | |
| Indio | 85,480 | 42 | 4 | Gross Alpha, Stage 2 DBP |
| Manteca | 84,958 | 10 | 1 | Stage 2 DBP |
| Goleta | 84,827 | 2 | 1 | Stage 2 DBP |
| Placentia | 84,292 | 0 | 0 | |
| Buena Park | 81,998 | 1 | 0 | |
| Milpitas | 81,839 | 6 | 0 | |
| Mountain View | 81,501 | 6 | 4 | Fecal Coliform |
| Upland | 81,487 | 6 | 2 | Gross Alpha |
| Inglewood | 80,824 | 4 | 0 | |
| Redlands | 78,377 | 16 | 7 | Contaminant 1028, Contaminant 1032, Stage 2 DBP |
| South Gate | 76,443 | 65 | 0 | |
| Chino Hills | 76,414 | 0 | 0 | |
| Compton | 76,377 | 10 | 4 | E. coli |
| Whittier | 74,954 | 2 | 0 | |
| Palm Springs | 74,837 | 74 | 5 | Gross Alpha, Selenium, Stage 2 DBP |
| Tulare | 74,320 | 90 | 52 | Gross Alpha, Selenium, Stage 2 DBP |
| Baldwin Park | 73,484 | 9 | 0 | |
| Turlock | 73,176 | 17 | 4 | Selenium, Stage 2 DBP |
| Calabasas | 72,602 | 0 | 0 | |
| Yuba City | 70,671 | 26 | 20 | Contaminant 2920, Total Haloacetic Acids (HAA5) |
| Palo Alto | 70,020 | 4 | 4 | E. coli, Fecal Coliform |
| Lodi | 69,927 | 21 | 7 | E. coli, Gross Alpha, TTHM +1 more |
| San Luis Obispo | 69,851 | 103 | 35 | Chlorine, E. coli, Selenium +1 more |
| Newport Beach | 69,136 | 12 | 1 | Chlorine |
| Watsonville | 68,078 | 113 | 23 | Contaminant 1032, Contaminant 2414, Gross Alpha +3 more |
| Citrus Heights | 67,878 | 2 | 0 | |
| Tustin | 67,226 | 9 | 1 | Nitrate |
| Lynwood | 66,967 | 5 | 0 | |
| Beaumont | 66,841 | 1 | 0 | |
| Lakewood | 66,135 | 0 | 0 | |
| Hanford | 65,603 | 93 | 52 | Gross Alpha, Haloacetic Acids, Stage 2 DBP +1 more |
| Woodland | 65,361 | 202 | 42 | Contaminant 1028, Gross Alpha, Selenium +1 more |
| Porterville | 65,168 | 111 | 72 | E. coli, Selenium, Stage 2 DBP |
| Brentwood | 65,022 | 76 | 51 | Barium, Selenium, Stage 2 DBP |
| Salinas | 64,442 | 567 | 439 | Barium, E. coli, Fecal Coliform +3 more |
| Novato | 63,992 | 3 | 1 | Stage 2 DBP |
| Laguna Beach | 63,469 | 2 | 0 | |
| La Habra | 63,118 | 0 | 0 | |
| Pico Rivera | 62,651 | 91 | 0 | |
| Pittsburg | 62,500 | 0 | 0 | |
| Petaluma | 61,570 | 17 | 1 | Stage 2 DBP |
| Gilroy | 60,126 | 21 | 7 | Selenium, Stage 2 DBP |
| Yucaipa | 60,098 | 30 | 13 | Gross Alpha, Selenium, TTHM |
| Grass Valley | 59,428 | 3 | 0 | |
| Fallbrook | 58,773 | 0 | 0 | |
| Truckee | 57,584 | 0 | 0 | |
| Fountain Valley | 56,747 | 2 | 0 | |
| Delano | 56,466 | 15 | 2 | Gross Alpha |
| Montclair | 56,017 | 1 | 0 | |
| Paramount | 55,200 | 1 | 0 | |
| Apple Valley | 55,188 | 210 | 108 | Barium, Gross Alpha, Lead +2 more |
| Rohnert Park | 54,984 | 1,157 | 3 | Chlorine Dioxide, Fecal Coliform |
| Camp Pendleton | 54,870 | 42 | 20 | Chlorine, Gross Alpha, TTHM |
| Ceres | 54,751 | 111 | 102 | Barium, Fecal Coliform, Gross Alpha +3 more |
| Rowland Heights | 54,660 | 0 | 0 | |
| Lincoln | 54,574 | 3 | 2 | Contaminant 2414 |
| Hollister | 53,795 | 107 | 38 | Barium, Contaminant 2920, Gross Alpha +4 more |
| West Sacramento | 53,355 | 2 | 1 | Stage 2 DBP |
| Thousand Oaks | 53,157 | 0 | 0 | |
| Lake Forest | 51,980 | 52 | 43 | Barium, Haloacetic Acids, Selenium +1 more |
| San Clemente | 51,607 | 5 | 0 | |
| Lompoc | 51,515 | 35 | 22 | Arsenic, Barium, Gross Alpha |
| Arcadia | 51,417 | 8 | 1 | Stage 2 DBP |
| Glendora | 49,934 | 3 | 0 | |
| Poway | 49,888 | 4 | 0 | |
| Colton | 49,425 | 30 | 6 | Gross Alpha |
| Los Banos | 48,604 | 57 | 53 | Contaminant 2920, Stage 2 DBP, TTHM |
| Brea | 48,479 | 0 | 0 | |
| El Centro | 47,589 | 45 | 17 | Stage 2 DBP, TTHM, Total Haloacetic Acids (HAA5) |
| Cerritos | 47,475 | 0 | 0 | |
| Bellflower | 47,429 | 2 | 0 | |
| Morgann Hill | 47,374 | 0 | 0 | |
| Oakley | 44,728 | 93 | 86 | Barium, Stage 2 DBP |
| Desert Hot Springs | 44,400 | 6 | 0 | |
| Elk Grove | 43,906 | 4 | 0 | |
| Coachella | 43,590 | 7 | 0 | |
| Adelanto | 43,049 | 73 | 1 | Stage 2 DBP |
| Lemoore | 42,658 | 200 | 181 | Fecal Coliform, Gross Alpha, TTHM +1 more |
| Ridgecrest | 41,650 | 2 | 0 | |
| Montebello | 41,575 | 3 | 0 | |
| San Bruno | 41,327 | 3 | 0 | |
| Carmichael | 41,193 | 3 | 0 | |
| Soquel | 40,809 | 0 | 0 | |
| Moorpark | 40,673 | 3 | 0 | |
| Beverly Hills | 40,547 | 14 | 0 | |
| Loma Linda | 40,497 | 7 | 0 | |
| Calexico | 40,427 | 34 | 5 | Fecal Coliform, Stage 2 DBP, TTHM |
| Lebec | 39,636 | 78 | 61 | Haloacetic Acids, TTHM |
| Livermore | 39,130 | 71 | 61 | Barium, Fecal Coliform |
| Pacifica | 38,546 | 0 | 0 | |
| Marina | 38,377 | 0 | 0 | |
| Julian | 37,963 | 119 | 25 | Contaminant 1028, Contaminant 1032, E. coli +2 more |
| Monrovia | 37,931 | 4 | 0 | |
| Sonora | 37,743 | 23 | 5 | E. coli, Gross Alpha, Stage 2 DBP +1 more |
| Vacaville | 37,513 | 71 | 67 | Fecal Coliform, Stage 2 DBP, TTHM +1 more |
| Ramona | 37,149 | 96 | 31 | Contaminant 4109, Haloacetic Acids, Selenium |
| Huntington Park | 37,117 | 7 | 0 | |
| Fair Oaks | 36,676 | 3 | 0 | |
| Foster City | 36,556 | 3 | 0 | |
| Stanford | 35,853 | 3 | 3 | Total Haloacetic Acids (HAA5) |
| La Crescenta | 35,841 | 0 | 0 | |
| Paso Robles | 35,803 | 130 | 105 | Arsenic, Barium, Lead +3 more |
| Lakeside | 35,500 | 7 | 0 | |
| Oroville | 35,433 | 37 | 5 | Mercury, Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Lathrop | 35,180 | 11 | 0 | |
| Atascadero | 35,158 | 9 | 0 | |
| San Andreas | 34,416 | 30 | 13 | Fecal Coliform, Gross Alpha, Stage 2 DBP +1 more |
| Tehachapi | 34,243 | 165 | 59 | Barium, Copper, Disinfection Byproducts +4 more |
| Ukiah | 33,008 | 25 | 2 | Chlorine, Fecal Coliform |
| Banning | 32,980 | 35 | 0 | |
| Santa Paula | 32,737 | 13 | 0 | |
| Manhattan Beach | 32,697 | 0 | 0 | |
| East Palo Alto | 32,419 | 3 | 2 | Fecal Coliform, Gross Alpha |
| La Verne | 31,580 | 92 | 3 | Selenium, Stage 2 DBP |
| Martinez | 31,478 | 3 | 0 | |
| Yucca Valley | 31,445 | 25 | 0 | |
| Imperial | 30,653 | 85 | 64 | Barium, Fecal Coliform, Stage 2 DBP +1 more |
| Granite Bay | 30,633 | 85 | 43 | Barium, Gross Alpha, Stage 2 DBP |
| Belmont | 30,609 | 2 | 2 | Fecal Coliform |
| Altadena | 30,150 | 2 | 0 | |
| Valley Center | 29,973 | 5 | 0 | |
| Atwater | 29,479 | 2 | 0 | |
| Norco | 29,368 | 105 | 0 | |
| Soledad | 29,120 | 31 | 12 | Chlorine Dioxide, Selenium, Stage 2 DBP |
| Phelan | 28,287 | 3 | 0 | |
| Vernon | 28,112 | 0 | 0 | |
| Eureka | 27,948 | 8 | 1 | Stage 2 DBP |
| Wasco | 27,929 | 64 | 30 | Barium, Gross Alpha |
| Big Bear Lake | 27,642 | 25 | 3 | Gross Alpha |
| Benicia | 27,131 | 2 | 0 | |
| Olivehurst | 27,059 | 4 | 0 | |
| Brawley | 26,862 | 6 | 0 | |
| Reedley | 26,731 | 19 | 2 | Stage 2 DBP |
| Oakdale | 26,711 | 57 | 3 | Barium, Stage 2 DBP |
| Galt | 26,591 | 17 | 10 | Barium, Stage 2 DBP |
| Sanger | 26,577 | 34 | 3 | Stage 2 DBP |
| Boulder Creek | 25,972 | 147 | 114 | E. coli, Fecal Coliform, Stage 2 DBP |
| Windsor | 25,561 | 3 | 0 | |
| South Pasadena | 25,389 | 5 | 2 | Barium |
| Patterson | 25,304 | 14 | 8 | Fecal Coliform, TTHM |
| Shafter | 24,969 | 24 | 5 | Gross Alpha, TTHM |
| Mountain House | 24,948 | 0 | 0 | |
| Seal Beach | 24,937 | 4 | 0 | |
| Riverbank | 24,884 | 51 | 48 | Barium, Selenium |
| Quartz Hill | 24,607 | 0 | 0 | |
| San Fernando | 23,946 | 0 | 0 | |
| Arroyo Grande | 23,710 | 152 | 102 | Arsenic, Barium, Selenium |
| Sutter Creek | 23,588 | 29 | 12 | Contaminant 2920, Disinfection Byproducts, Fecal Coliform +1 more |
| Chico | 23,374 | 639 | 378 | Contaminant 1022, E. coli, Fecal Coliform +6 more |
| El Verano | 23,187 | 10 | 0 | |
| Millbrae | 22,845 | 4 | 1 | Stage 2 DBP |
| Corcoran | 22,808 | 14 | 4 | Gross Alpha |
| Cudahy | 22,700 | 74 | 0 | |
| Menlo Park | 22,562 | 3 | 2 | Fecal Coliform |
| Arcata | 22,549 | 3 | 0 | |
| Marysville | 22,264 | 60 | 9 | Barium, Contaminant 1028, Contaminant 1032 +2 more |
| Temescal Valley | 21,971 | 1 | 0 | |
| Port Hueneme | 21,775 | 8 | 0 | |
| Rancho Santa Fe | 21,578 | 0 | 0 | |
| Anderson | 21,515 | 23 | 7 | Chlorine, Fecal Coliform, Stage 2 DBP |
| American Canyon | 21,437 | 19 | 18 | TTHM |
| Crescent City | 20,897 | 24 | 8 | E. coli, Fecal Coliform, Stage 2 DBP |
| Taft | 20,500 | 3 | 0 | |
| Norwalk | 20,283 | 0 | 0 | |
| Lomita | 20,256 | 2 | 1 | TTHM |
| Grand Terrace | 20,188 | 1 | 0 | |
| Cutten | 19,807 | 0 | 0 | |
| Arvin | 19,669 | 254 | 133 | Barium, Gross Alpha, Stage 2 DBP +1 more |
| Lamont | 19,602 | 48 | 39 | Barium, Gross Alpha |
| San Jacinto | 19,450 | 10 | 0 | |
| Chowchilla | 19,272 | 26 | 16 | Barium |
| Santa Fe Springs | 19,219 | 2 | 0 | |
| Greenfield | 19,208 | 25 | 14 | Fecal Coliform, Stage 2 DBP |
| Half Moon Bay | 18,940 | 15 | 0 | |
| Twentynine Palms | 18,795 | 1 | 1 | Gross Alpha |
| Mckinleyville | 18,745 | 4 | 0 | |
| Sausalito | 18,447 | 2 | 0 | |
| Coalinga | 18,440 | 599 | 570 | Barium, Fecal Coliform, Gross Alpha +2 more |
| Rosamond | 18,134 | 148 | 134 | Barium, Haloacetic Acids, Stage 2 DBP |
| Oak View | 17,937 | 7 | 4 | Fecal Coliform, Total Haloacetic Acids (HAA5) |
| Kerman | 17,281 | 19 | 1 | Stage 2 DBP |
| Lakeport | 17,195 | 22 | 5 | Fecal Coliform, Selenium, Stage 2 DBP |
| Crestline | 17,005 | 19 | 2 | Stage 2 DBP |
| Fillmore | 16,987 | 30 | 3 | Gross Alpha, Stage 2 DBP |
| Orangevale | 16,861 | 0 | 0 | |
| Discovery Bay | 16,790 | 0 | 0 | |
| Pinedale | 16,736 | 3 | 0 | |
| El Segundo | 16,445 | 2 | 0 | |
| Blythe | 16,357 | 81 | 5 | E. coli, Total Haloacetic Acids (HAA5) |
| Moffett Field | 16,273 | 3 | 3 | Fecal Coliform |
| Carpinteria | 16,062 | 2 | 2 | Gross Alpha |
| La Palma | 15,948 | 2 | 0 | |
| Red Bluff | 15,885 | 67 | 14 | Gross Alpha, Stage 2 DBP |
| Ripon | 15,766 | 9 | 0 | |
| Fort Irwin | 15,701 | 183 | 180 | Barium, Lead |
| Rio Linda | 15,460 | 4 | 3 | Gross Alpha |
| 29 Palms | 15,248 | 9 | 4 | Gross Alpha |
| Vandenberg Sfb | 14,971 | 1 | 1 | TTHM |
| Livingston | 14,894 | 16 | 13 | Barium, Contaminant 2414, Stage 2 DBP |
| Point Mugu | 14,579 | 8 | 1 | TTHM |
| Parlier | 14,576 | 3 | 1 | Stage 2 DBP |
| La Puente | 14,401 | 0 | 0 | |
| California City | 14,290 | 6 | 2 | TTHM |
| Mcfarland | 14,161 | 68 | 28 | Barium, Gross Alpha, Selenium |
| Morro Bay | 14,125 | 5 | 3 | Selenium |
| Jamul | 14,010 | 52 | 30 | Contaminant 4109, E. coli, Haloacetic Acids +1 more |
| Westlake Village | 13,923 | 1 | 0 | |
| Susanville | 13,892 | 0 | 0 | |
| Kingsburg | 13,851 | 94 | 35 | Gross Alpha |
| Nipomo | 13,771 | 0 | 0 | |
| Clearlake | 13,700 | 13 | 10 | TTHM, Total Haloacetic Acids (HAA5) |
| Avenal | 13,696 | 46 | 38 | Gross Alpha, Stage 2 DBP, TTHM +1 more |
| Trabuco Canyon | 13,659 | 1 | 1 | Fecal Coliform |
| South San Francisco | 13,511 | 2 | 0 | |
| Sonoma | 13,206 | 17 | 1 | Stage 2 DBP |
| Palomar Mtn Road | 13,050 | 5 | 0 | |
| Grover Beach | 12,841 | 89 | 74 | Barium |
| Scotts Valley | 12,799 | 18 | 2 | Fecal Coliform, Stage 2 DBP |
| Tahoe City | 12,790 | 14 | 2 | Fecal Coliform, Stage 2 DBP |
| Big Bear City | 12,738 | 0 | 0 | |
| Linsday | 12,659 | 175 | 173 | Contaminant 2931, E. coli, TTHM +1 more |
| Dixon | 12,540 | 0 | 0 | |
| Fortuna | 12,538 | 14 | 2 | Stage 2 DBP |
| Maywood | 12,408 | 2 | 0 | |
| Newman | 12,207 | 14 | 5 | Gross Alpha, Selenium |
| Hillsborough | 11,926 | 6 | 0 | |
| Signal Hill | 11,848 | 13 | 11 | Fecal Coliform |
| Exeter | 11,787 | 16 | 3 | Selenium, Stage 2 DBP |
| Calimesa | 11,641 | 44 | 0 | |
| Healdsburg | 11,619 | 17 | 0 | |
| Ojai | 11,575 | 39 | 12 | E. coli, Fecal Coliform, Stage 2 DBP +1 more |
| Mendota | 11,404 | 11 | 3 | Gross Alpha |
| Edwards Afb | 11,316 | 6 | 3 | E. coli |
| Cloverdale | 11,061 | 8 | 3 | Gross Alpha, Stage 2 DBP |
| Sierra Madre | 11,000 | 0 | 0 | |
| Farmersville | 10,743 | 10 | 1 | Stage 2 DBP |
| Shasta Lake | 10,657 | 0 | 0 | |
| Three Rivers | 10,513 | 208 | 128 | Barium, E. coli, Fecal Coliform +4 more |
| Rio Vista | 10,489 | 2 | 0 | |
| Waterford | 10,464 | 0 | 0 | |
| Willits | 10,382 | 30 | 12 | Fecal Coliform, TTHM, Total Haloacetic Acids (HAA5) |
| Royal Oaks | 10,349 | 140 | 119 | Barium, Contaminant 2414, Gross Alpha +1 more |
| La Canada Flintridge | 10,070 | 4 | 0 | |
| Santa Ysabel | 9,913 | 39 | 1 | E. coli |
| Guerneville | 9,835 | 3 | 0 | |
| Bishop | 9,798 | 125 | 27 | Gross Alpha, Haloacetic Acids, Nitrate-Nitrite +1 more |
| Winton | 9,745 | 8 | 5 | Contaminant 2414, Stage 2 DBP |
| Georgetown | 9,614 | 45 | 2 | Gross Alpha |
| Orange Cove | 9,525 | 10 | 5 | Gross Alpha, Stage 2 DBP |
| Bermuda Dunes | 9,445 | 0 | 0 | |
| Forestville | 9,361 | 84 | 8 | Contaminant 1022, Disinfection Byproducts, Fecal Coliform |
| La Canada | 9,325 | 3 | 0 | |
| Live Oak | 9,318 | 4 | 0 | |
| Huron | 9,306 | 38 | 34 | Contaminant 2920, Fecal Coliform, Gross Alpha +2 more |
| Needles | 9,297 | 16 | 0 | |
| Paradise | 9,142 | 0 | 0 | |
| Mammoth Lakes | 8,979 | 52 | 44 | Contaminant 4109, Fecal Coliform, Gross Alpha +1 more |
| Guadalupe | 8,897 | 1 | 0 | |
| Pismo Beach | 8,636 | 13 | 10 | Total Haloacetic Acids (HAA5) |
| Firebaugh | 8,616 | 115 | 85 | Barium, Contaminant 1032, Contaminant 4109 +6 more |
| Templeton | 8,556 | 2 | 0 | |
| Corning | 8,541 | 10 | 6 | Gross Alpha, Stage 2 DBP |
| Gonzales | 8,427 | 63 | 47 | Selenium, Stage 2 DBP |
| Santa Ynez | 8,409 | 6 | 1 | Fecal Coliform |
| Sebastopol | 8,387 | 20 | 7 | Fecal Coliform, Stage 2 DBP |
| Orosi | 8,300 | 0 | 0 | |
| Orland | 8,298 | 4 | 0 | |
| Lancaster | 8,296 | 608 | 285 | Barium, Gross Alpha, Nitrate +2 more |
| Dinuba | 8,215 | 35 | 17 | Gross Alpha, Stage 2 DBP |
| Yreka | 8,214 | 13 | 2 | Stage 2 DBP |
| Earlimart | 8,210 | 53 | 35 | Barium, E. coli, Gross Alpha +1 more |
| Fort Bragg | 8,059 | 25 | 5 | Fecal Coliform, Gross Alpha, Stage 2 DBP |
| Castroville | 7,943 | 74 | 57 | Selenium |
| Lake Almanor | 7,874 | 4 | 1 | Stage 2 DBP |
| Lake Arrowhead | 7,855 | 0 | 0 | |
| Kirkwood | 7,851 | 2 | 0 | |
| Woodlake | 7,846 | 12 | 2 | Gross Alpha |
| Delhi | 7,784 | 6 | 0 | |
| West Covina | 7,775 | 0 | 0 | |
| Los Osos | 7,677 | 1 | 0 | |
| Oceano | 7,601 | 2 | 0 | |
| Hughson | 7,531 | 120 | 118 | Barium, Contaminant 2414, Gross Alpha +1 more |
| Represa | 7,502 | 2 | 1 | Stage 2 DBP |
| Fowler | 7,494 | 13 | 0 | |
| Dos Palos | 7,452 | 44 | 43 | Contaminant 2920, Fecal Coliform, TTHM +1 more |
| Escalon | 7,429 | 0 | 0 | |
| Cotati | 7,379 | 0 | 0 | |
| Tahoe Vista | 7,352 | 2 | 2 | Fecal Coliform |
| Solvang | 7,337 | 25 | 1 | Contaminant 1039 |
| Gridley | 7,269 | 6 | 1 | Stage 2 DBP |
| Cottonwood | 7,140 | 11 | 3 | E. coli, Stage 2 DBP |
| Winters | 7,115 | 1 | 0 | |
| Castaic | 7,000 | 0 | 0 | |
| Heber | 6,979 | 10 | 7 | TTHM, Total Haloacetic Acids (HAA5) |
| Kelseyville | 6,939 | 36 | 18 | E. coli, TTHM, Total Haloacetic Acids (HAA5) |
| Foresthill | 6,932 | 7 | 1 | Stage 2 DBP |
| Jackson | 6,819 | 12 | 6 | Disinfection Byproducts, TTHM |
| Beale Afb | 6,785 | 6 | 1 | Gross Alpha |
| Nuevo | 6,733 | 11 | 10 | TTHM |
| Joshua Tree | 6,640 | 6 | 6 | Gross Alpha |
| China Lake | 6,600 | 9 | 3 | Gross Alpha |
| Colusa | 6,487 | 12 | 1 | Stage 2 DBP |
| Holtville | 6,385 | 73 | 68 | Stage 2 DBP, TTHM, Total Haloacetic Acids (HAA5) |
| Helendale | 6,347 | 46 | 42 | Barium |
| St. Helena | 6,328 | 33 | 27 | Fecal Coliform, Total Haloacetic Acids (HAA5) |
| Idyllwild | 6,319 | 29 | 8 | E. coli, Gross Alpha, TTHM +1 more |
| Los Altos Hills | 6,245 | 3 | 0 | |
| Hidden Valley Lake | 6,235 | 1 | 1 | Gross Alpha |
| Gustine | 6,230 | 10 | 3 | Gross Alpha, Stage 2 DBP |
| Cutler | 6,200 | 28 | 27 | Contaminant 2931, Selenium, Stage 2 DBP |
| Coarsegold | 6,160 | 83 | 51 | Contaminant 1028, Contaminant 1032, E. coli +2 more |
| Montara | 6,078 | 3 | 0 | |
| Calistoga | 5,810 | 40 | 37 | TTHM, Total Haloacetic Acids (HAA5) |
| Rancho Murieta | 5,728 | 12 | 6 | Fecal Coliform, TTHM |
| Meadow Vista | 5,674 | 1 | 0 | |
| Keyes | 5,672 | 110 | 110 | Barium |
| Villa Park | 5,659 | 0 | 0 | |
| Running Springs | 5,638 | 15 | 3 | E. coli, Gross Alpha |
| Weed | 5,595 | 22 | 5 | Gross Alpha, Stage 2 DBP |
| Williams | 5,593 | 0 | 0 | |
| June Lake | 5,573 | 18 | 12 | Fecal Coliform, Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Cambria | 5,532 | 8 | 7 | Fecal Coliform |
| Arnold | 5,527 | 7 | 3 | Mercury, Total Haloacetic Acids (HAA5) |
| Hilmar | 5,504 | 2 | 0 | |
| La Habra Heights | 5,325 | 0 | 0 | |
| Buellton | 5,306 | 10 | 5 | Arsenic, Barium |
| Carnelian Bay | 5,093 | 51 | 4 | Disinfection Byproducts, Fecal Coliform, Stage 2 DBP |
| Denair | 5,090 | 4 | 0 | |
| Brisbane | 4,874 | 6 | 3 | Total Haloacetic Acids (HAA5) |
| Frazier Park | 4,783 | 65 | 41 | Barium, Selenium, Stage 2 DBP |
| Murphys | 4,774 | 11 | 10 | TTHM |
| Mojave | 4,755 | 55 | 48 | Barium, Chlorine |
| Mt. Shasta | 4,749 | 37 | 22 | E. coli, Gross Alpha, Stage 2 DBP |
| Cayucos | 4,748 | 0 | 0 | |
| Visalia | 4,668 | 129 | 71 | E. coli, Gross Alpha, Selenium +1 more |
| Ivanhoe | 4,580 | 4 | 1 | Stage 2 DBP |
| Palomar Mountain | 4,416 | 7 | 0 | |
| La Grange | 4,281 | 7 | 1 | Stage 2 DBP |
| Cobb | 4,208 | 18 | 2 | Stage 2 DBP |
| Planada | 4,164 | 6 | 1 | Stage 2 DBP |
| Portola | 4,146 | 38 | 25 | Haloacetic Acids, Stage 2 DBP |
| Armona | 4,143 | 77 | 71 | Barium, Gross Alpha, TTHM |
| Angels Camp | 4,124 | 34 | 20 | Contaminant 2920, E. coli, Gross Alpha +3 more |
| Wheatland | 4,124 | 4 | 0 | |
| Jamestown | 4,119 | 26 | 15 | E. coli, Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Weaverville | 4,077 | 14 | 9 | Fecal Coliform |
| San Joaquin | 4,060 | 2 | 0 | |
| Wildomar | 4,026 | 5 | 0 | |
| Lockeford | 3,930 | 9 | 0 | |
| Quincy | 3,928 | 7 | 6 | E. coli |
| Del Mar | 3,919 | 4 | 0 | |
| Avalon | 3,822 | 0 | 0 | |
| Yountville | 3,787 | 9 | 1 | Stage 2 DBP |
| Ione | 3,774 | 8 | 1 | Fecal Coliform |
| Mariposa | 3,755 | 53 | 40 | Gross Alpha, Stage 2 DBP, TTHM +1 more |
| Aptos | 3,712 | 1 | 0 | |
| San Francisco | 3,643 | 197 | 93 | Chlorine Dioxide, Fecal Coliform |
| Los Gatos | 3,587 | 218 | 125 | Contaminant 1011, E. coli, Fecal Coliform +2 more |
| Chester | 3,581 | 2 | 2 | E. coli |
| Alturas | 3,577 | 4 | 2 | Stage 2 DBP |
| Esparto | 3,574 | 6 | 3 | Gross Alpha |
| Twain Harte | 3,500 | 15 | 2 | Stage 2 DBP |
| Groveland | 3,485 | 7 | 3 | Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Nevada City | 3,457 | 66 | 9 | E. coli |
| Borrego Springs | 3,429 | 4 | 0 | |
| Strathmore | 3,424 | 38 | 14 | Nitrate-Nitrite, Selenium, Stage 2 DBP |
| Angwin | 3,390 | 95 | 66 | Stage 2 DBP, TTHM, Total Haloacetic Acids (HAA5) |
| Moreno Valley | 3,382 | 2 | 0 | |
| Aromas | 3,363 | 16 | 7 | Gross Alpha, Stage 2 DBP, Surface Water Treatment |
| Rio Dell | 3,300 | 0 | 0 | |
| Lucerne Valley | 3,277 | 116 | 50 | Gross Alpha, Selenium, Stage 2 DBP |
| Avila Beach | 3,230 | 5 | 5 | TTHM |
| Burney | 3,154 | 2 | 1 | Gross Alpha |
| Seaside | 3,150 | 1 | 0 | |
| Shasta | 3,069 | 0 | 0 | |
| Bloomington | 3,055 | 1 | 1 | Gross Alpha |
| Boron | 3,054 | 117 | 80 | Barium |
| Littlerock | 3,040 | 25 | 0 | |
| Talmage | 3,029 | 29 | 7 | Gross Alpha, Stage 2 DBP |
| Green Valley Lake | 2,993 | 10 | 4 | Gross Alpha, Haloacetic Acids |
| Independence | 2,943 | 54 | 4 | Chlorine Dioxide, Stage 2 DBP |
| Nice | 2,929 | 0 | 0 | |
| Twin Peaks | 2,915 | 9 | 0 | |
| Sutter | 2,904 | 1 | 1 | Gross Alpha |
| Pine Valley | 2,900 | 31 | 15 | Haloacetic Acids |
| Riverdale | 2,836 | 128 | 120 | Barium, Fecal Coliform, Gross Alpha +3 more |
| Arbuckle | 2,778 | 4 | 0 | |
| Pixley | 2,772 | 41 | 28 | Barium, Gross Alpha |
| Brownsville | 2,772 | 1 | 0 | |
| Dublin | 2,753 | 0 | 0 | |
| Springville | 2,752 | 54 | 42 | Barium, E. coli, Selenium +1 more |
| Valley Springs | 2,725 | 8 | 4 | Total Haloacetic Acids (HAA5) |
| Caruthers | 2,718 | 134 | 120 | Barium, Contaminant 2946, Gross Alpha |
| Terra Bella | 2,656 | 49 | 42 | TTHM, Total Haloacetic Acids (HAA5) |
| Skyforest | 2,654 | 3 | 0 | |
| Mi Wuk Village | 2,630 | 7 | 1 | Stage 2 DBP |
| San Miguel | 2,600 | 0 | 0 | |
| Gualala | 2,593 | 5 | 2 | Fecal Coliform |
| Smith River | 2,568 | 4 | 0 | |
| Pauma Valley | 2,555 | 175 | 121 | Arsenic, Bromate, E. coli +3 more |
| Tipton | 2,543 | 18 | 17 | Selenium |
| San Juan Bautista | 2,530 | 34 | 7 | Nitrate-Nitrite, Selenium, Stage 2 DBP |
| Bolinas | 2,483 | 48 | 48 | Fecal Coliform, TTHM, Total Haloacetic Acids (HAA5) |
| Cedarpines Park | 2,458 | 10 | 10 | Gross Alpha, Selenium |
| Lost Hills | 2,370 | 31 | 6 | Gross Alpha |
| Clearlake Oak | 2,359 | 11 | 6 | TTHM |
| Hayfork | 2,324 | 2 | 0 | |
| Bradley | 2,241 | 105 | 65 | TTHM, Total Haloacetic Acids (HAA5) |
| Santa Nella | 2,211 | 3 | 2 | TTHM |
| Pine Grove | 2,209 | 14 | 8 | Disinfection Byproducts, Stage 2 DBP, TTHM +1 more |
| Westmorland | 2,202 | 12 | 8 | Stage 2 DBP, TTHM |
| Pine Mountain Club | 2,200 | 0 | 0 | |
| Alpine Meadows | 2,200 | 0 | 0 | |
| Poplar | 2,200 | 4 | 2 | Selenium |
| Garberville | 2,180 | 51 | 9 | E. coli, Fecal Coliform, Stage 2 DBP |
| Bridgeport | 2,148 | 160 | 93 | Barium, Gross Alpha, Stage 2 DBP |
| Herlong | 2,114 | 1 | 0 | |
| Carmel | 2,076 | 63 | 41 | Fecal Coliform, Lead, Stage 2 DBP |
| Middletown | 2,070 | 72 | 38 | E. coli, Stage 2 DBP, Total Haloacetic Acids (HAA5) |
| Westwood | 2,062 | 0 | 0 | |
| Biggs | 2,060 | 9 | 1 | Stage 2 DBP |
| Big Sur | 2,046 | 62 | 43 | Fecal Coliform |
| Big Pine | 2,017 | 16 | 2 | Gross Alpha, Stage 2 DBP |
| Cabazon | 2,010 | 4 | 0 | |
| Gerber | 2,004 | 13 | 3 | Stage 2 DBP |
| Midway City | 2,000 | 4 | 0 | |
| Dunsmuir | 1,875 | 14 | 5 | Chlorine, E. coli, Stage 2 DBP |
| Arrowbear Lake | 1,856 | 3 | 1 | Gross Alpha |
| Yosemite Np | 1,836 | 17 | 3 | Contaminant 1022, Disinfection Byproducts |
| Mt. Baldy | 1,819 | 22 | 6 | Gross Alpha |
| Trona | 1,818 | 1 | 0 | |
| Elizabeth Lake | 1,790 | 3 | 1 | TTHM |
| Claremont | 1,789 | 11 | 0 | |
| Linden | 1,784 | 1 | 0 | |
| Cold Springs | 1,771 | 1 | 0 | |
| Trinidad | 1,770 | 35 | 21 | Fecal Coliform, Surface Water Treatment, TTHM +1 more |
| Le Grand | 1,739 | 14 | 13 | Barium, Stage 2 DBP |
| Blairsden | 1,734 | 76 | 36 | Barium, Stage 2 DBP |
| Kernville | 1,733 | 35 | 22 | Barium, Contaminant 1032, E. coli +1 more |
| Yorba Linda | 1,729 | 13 | 2 | Gross Alpha |
| Seeley | 1,729 | 76 | 69 | Fecal Coliform, Stage 2 DBP, TTHM +1 more |
| Biola | 1,623 | 12 | 2 | Gross Alpha |
| Richgrove | 1,617 | 88 | 15 | Barium, Contaminant 2931, Gross Alpha +2 more |
| Inyokern | 1,608 | 244 | 4 | E. coli, Selenium, Stage 2 DBP |
| Oakhurst | 1,582 | 236 | 125 | Barium, Contaminant 1028, Contaminant 4109 +5 more |
| Durham | 1,581 | 3 | 0 | |
| Lower Lake | 1,579 | 25 | 1 | Gross Alpha |
| Devore | 1,574 | 25 | 6 | Selenium |
| Weldon | 1,562 | 183 | 161 | Barium, Disinfection Byproducts, E. coli +4 more |
| Point Reyes Station | 1,560 | 85 | 0 | |
| Shingletown | 1,539 | 5 | 1 | Stage 2 DBP |
| Fall River Mills | 1,535 | 2 | 1 | Gross Alpha |
| Buttonwillow | 1,534 | 32 | 11 | Gross Alpha |
| Los Alamos | 1,534 | 4 | 0 | |
| Angelus Oaks | 1,520 | 26 | 6 | E. coli, Stage 2 DBP |
| Hume | 1,519 | 6 | 6 | Fecal Coliform, Gross Alpha |
| Downieville | 1,509 | 6 | 3 | E. coli, Stage 2 DBP |
| Del Rey | 1,491 | 27 | 3 | Gross Alpha |
| Tulelake | 1,485 | 14 | 2 | Stage 2 DBP |
| Graeagle | 1,478 | 2 | 1 | Stage 2 DBP |
| North Edwards | 1,462 | 253 | 203 | Barium |
| Forest Falls | 1,452 | 41 | 2 | Stage 2 DBP |
| Los Molinos | 1,450 | 52 | 50 | Barium, Gross Alpha |
| Inverness | 1,445 | 23 | 20 | TTHM, Total Haloacetic Acids (HAA5) |
| La Honda | 1,418 | 143 | 9 | E. coli, Total Haloacetic Acids (HAA5) |
| Plymouth | 1,399 | 41 | 7 | Disinfection Byproducts, TTHM |
| Grizzly Flats | 1,374 | 14 | 0 | |
| Bethel Island | 1,366 | 15 | 2 | Stage 2 DBP |
| Hydesville | 1,366 | 18 | 1 | Stage 2 DBP |
| Barstow | 1,364 | 134 | 120 | Barium, Stage 2 DBP |
| Bodega Bay | 1,357 | 3 | 0 | |
| Mccloud | 1,317 | 9 | 4 | E. coli, Stage 2 DBP |
| Laton | 1,313 | 50 | 42 | Barium, Gross Alpha, Selenium +1 more |
| Felton | 1,303 | 29 | 16 | Bromate, E. coli, Fecal Coliform +1 more |
| Willow Creek | 1,298 | 7 | 5 | E. coli, Fecal Coliform, Stage 2 DBP |
| Pinecrest | 1,298 | 3 | 1 | Stage 2 DBP |
| Green Valley | 1,275 | 2 | 1 | Stage 2 DBP |
| Montague | 1,264 | 14 | 13 | E. coli, Stage 2 DBP, TTHM +1 more |
| Kettleman City | 1,242 | 133 | 120 | Barium, Gross Alpha, Stage 2 DBP +1 more |
| Redway | 1,207 | 3 | 1 | Fecal Coliform |
| Trinity Center | 1,206 | 22 | 4 | Fecal Coliform, Stage 2 DBP |
| Mount Hermon | 1,176 | 5 | 1 | Stage 2 DBP |
| Maxwell | 1,175 | 2 | 0 | |
| Blue Lake | 1,172 | 0 | 0 | |
| Camp Meeker | 1,171 | 0 | 0 | |
| Olympic Valley | 1,165 | 0 | 0 | |
| Sea Ranch | 1,160 | 6 | 1 | Stage 2 DBP |
| Dillon Beach | 1,152 | 30 | 26 | TTHM, Total Haloacetic Acids (HAA5) |
| Laytonville | 1,152 | 0 | 0 | |
| Upper Lake | 1,139 | 6 | 1 | Stage 2 DBP |
| Happy Camp | 1,100 | 7 | 2 | Fecal Coliform, Stage 2 DBP |
| Platina | 1,055 | 3 | 1 | Stage 2 DBP |
| Friant | 1,046 | 15 | 0 | |
| Saratoga | 1,019 | 48 | 1 | E. coli |
| Paicines | 1,017 | 31 | 11 | E. coli, Gross Alpha, Lead |
| Sultana | 1,014 | 78 | 52 | E. coli, Selenium, Stage 2 DBP |
| Baker | 1,000 | 9 | 0 | |
| Lindsay | 1,000 | 105 | 91 | Fecal Coliform, Nitrate-Nitrite, Selenium +3 more |
| Loyalton | 983 | 3 | 0 | |
| Greenville | 980 | 5 | 3 | Chlorine, Fecal Coliform, Stage 2 DBP |
| North Highlands | 962 | 3 | 0 | |
| San Martin | 961 | 7 | 1 | Gross Alpha |
| Occidental | 951 | 13 | 0 | |
| Whitethorn | 919 | 38 | 35 | E. coli, Fecal Coliform |
| Scotia | 906 | 7 | 4 | E. coli, Fecal Coliform, Stage 2 DBP |
| Dorris | 887 | 4 | 1 | Stage 2 DBP |
| Madison | 876 | 21 | 2 | Selenium, Stage 2 DBP |
| Alpaugh | 871 | 110 | 96 | Barium |
| Shaver Lake | 850 | 10 | 0 | |
| Llano | 845 | 11 | 3 | Stage 2 DBP |
| Lake Arrowhead Ca 92352 | 845 | 1 | 0 | |
| Clio | 844 | 3 | 1 | Stage 2 DBP |
| Loleta | 828 | 6 | 4 | Cadmium, Gross Alpha |
| Tranquillity | 807 | 41 | 19 | Gross Alpha, Stage 2 DBP |
| Monterey | 803 | 40 | 5 | E. coli, Stage 2 DBP |
| Eldorado Hills | 800 | 12 | 5 | Fecal Coliform, Mercury |
| Daggett | 795 | 44 | 41 | Haloacetic Acids |
| La Selva Beach | 778 | 6 | 0 | |
| Anza | 776 | 80 | 30 | Selenium, Stage 2 DBP |
| Reno | 756 | 0 | 0 | |
| Phillipsville | 748 | 60 | 22 | E. coli, Fecal Coliform, Stage 2 DBP |
| Lee Vining | 742 | 4 | 0 | |
| Lakehead | 732 | 8 | 3 | Fecal Coliform, Stage 2 DBP |
| Orleans | 721 | 33 | 21 | Bromate, E. coli, Fecal Coliform +2 more |
| Etna | 720 | 4 | 0 | |
| New Cuyama | 700 | 9 | 0 | |
| Fort Jones | 695 | 6 | 0 | |
| Salyer | 693 | 26 | 14 | Chlorine, E. coli, Fecal Coliform +1 more |
| Clayton | 680 | 3 | 1 | Gross Alpha |
| Junction City | 677 | 11 | 7 | E. coli, Fecal Coliform |
| Campo | 670 | 9 | 1 | Stage 2 DBP |
| Gasquet | 657 | 9 | 2 | Fecal Coliform |
| Saugus | 657 | 0 | 0 | |
| Klamath | 656 | 10 | 4 | E. coli, Stage 2 DBP |
| Mineral | 634 | 8 | 1 | Stage 2 DBP |
| Mountain Pass | 626 | 3 | 1 | Stage 2 DBP |
| Bear Valley | 625 | 29 | 29 | Disinfection Byproducts, Fecal Coliform, Total Haloacetic Acids (HAA5) |
| Isleton | 625 | 64 | 49 | Barium, E. coli, Fecal Coliform +1 more |
| Ducor | 616 | 7 | 2 | Selenium, Stage 2 DBP |
| Cedarville | 600 | 0 | 0 | |
| Mount Baldy | 600 | 1 | 0 | |
| Lake Isabella | 594 | 279 | 106 | Barium, Disinfection Byproducts, E. coli +2 more |
| Palo Verde | 585 | 22 | 8 | Barium, Chlorine, Haloacetic Acids +2 more |
| Stinson Beach | 583 | 3 | 1 | Disinfection Byproducts |
| San Ardo | 575 | 2 | 1 | Stage 2 DBP |
| River Pines | 574 | 5 | 1 | Stage 2 DBP |
| Crows Landing | 570 | 9 | 2 | Stage 2 DBP |
| Jacumba | 561 | 2 | 0 | |
| Mountain Center | 551 | 22 | 1 | E. coli |
| Chiriaco Summit | 544 | 10 | 0 | |
| Crowley Lake | 526 | 18 | 1 | Stage 2 DBP |
| Grimes | 512 | 152 | 135 | Barium |
| Carmel Valley | 504 | 13 | 0 | |
| Ludlow | 500 | 129 | 119 | Barium, Contaminant 1032, Contaminant 4109 +2 more |
| City of Colusa | 496 | 10 | 0 | |
| Miranda | 492 | 1 | 0 | |
| Sky Forest | 492 | 13 | 0 | |
| Tehama | 483 | 2 | 0 | |
| Lytle Creek | 475 | 1 | 0 | |
| Shingletoown | 475 | 2 | 1 | Stage 2 DBP |
| Morgan Hill | 468 | 48 | 11 | Contaminant 1094, E. coli, Gross Alpha +2 more |
| Bodfish | 465 | 14 | 4 | E. coli, Stage 2 DBP |
| San Simeon | 462 | 8 | 8 | Fecal Coliform |
| Mendocino | 459 | 91 | 88 | Gross Alpha, TTHM, Total Haloacetic Acids (HAA5) |
| Point Arena | 459 | 5 | 0 | |
| Mentone | 451 | 70 | 1 | Stage 2 DBP |
| Bieber | 450 | 0 | 0 | |
| Wilton | 445 | 0 | 0 | |
| Edison | 438 | 42 | 39 | Nitrate-Nitrite, Selenium, Stage 2 DBP |
| Winterhaven | 434 | 128 | 3 | E. coli, Stage 2 DBP |
| San Juan Capistrano | 429 | 13 | 0 | |
| San Leandro | 420 | 0 | 0 | |
| Death Valley | 413 | 8 | 0 | |
| Tampa | 413 | 4 | 0 | |
| Paynes Creek | 412 | 6 | 1 | Stage 2 DBP |
| Muir Beach | 411 | 2 | 1 | Stage 2 DBP |
| Ferndale | 408 | 13 | 0 | |
| Penn Valley | 400 | 11 | 2 | Gross Alpha, Stage 2 DBP |
| Potrero | 400 | 89 | 72 | Barium |
| Mi-Wuk Village | 400 | 7 | 5 | Contaminant 1028, Contaminant 1032, Stage 2 DBP |
| Orick | 396 | 0 | 0 | |
| Norden | 384 | 3 | 0 | |
| Princeton | 382 | 5 | 0 | |
| North Fork | 382 | 130 | 118 | Barium, Contaminant 1028, Contaminant 1032 +3 more |
| Eugene | 382 | 0 | 0 | |
| Elk | 380 | 4 | 1 | Stage 2 DBP |
| Westport | 369 | 4 | 1 | Fecal Coliform |
| Moss Landing | 363 | 4 | 0 | |
| Cazadero | 360 | 15 | 1 | Fecal Coliform |
| Scottsdale | 353 | 3 | 1 | Stage 2 DBP |
| Desert Center | 350 | 1 | 0 | |
| Tres Pinos | 350 | 2 | 0 | |
| Prather | 345 | 2 | 0 | |
| Santa Clarita | 344 | 10 | 5 | Selenium, Stage 2 DBP |
| Wofford Heights | 338 | 99 | 87 | Barium, Haloacetic Acids, Selenium +1 more |
| Blue Jay | 333 | 9 | 0 | |
| Myers Flat | 330 | 5 | 1 | Stage 2 DBP |
| Washington | 330 | 7 | 2 | Bromate, Stage 2 DBP |
| Pescadero | 328 | 106 | 11 | Contaminant 1041, Copper, E. coli +4 more |
| Chandler | 325 | 2 | 0 | |
| Thermal | 316 | 20 | 7 | Barium, Stage 2 DBP |
| Larkspur | 316 | 3 | 1 | Gross Alpha |
| San Lucas | 315 | 10 | 6 | Selenium |
| Soda Springs | 310 | 14 | 11 | Fecal Coliform |
| Walnut Grove | 308 | 74 | 63 | Barium, E. coli, Gross Alpha +1 more |
| Johanesburg | 303 | 74 | 61 | Barium, Stage 2 DBP |
| Glenhaven | 300 | 2 | 0 | |
| Greenbrae | 300 | 4 | 0 | |
| Palo Cedro | 300 | 6 | 1 | Stage 2 DBP |
| Penngrove | 300 | 4 | 0 | |
| King City | 299 | 8 | 0 | |
| Hercules | 299 | 4 | 2 | Stage 2 DBP |
| Berry Creek | 297 | 6 | 0 | |
| Geyserville | 290 | 1 | 0 | |
| Grenada | 289 | 5 | 4 | E. coli, Selenium |
| Snelling | 286 | 2 | 2 | TTHM |
| Mount Hamilton | 284 | 1 | 0 | |
| Valencia | 282 | 57 | 47 | Barium, Stage 2 DBP |
| Standard | 282 | 4 | 1 | Gross Alpha |
| Hornbrook | 280 | 8 | 5 | Chlorine, Fecal Coliform, Stage 2 DBP |
| Los Olivos | 279 | 4 | 2 | Gross Alpha |
| Orinda | 277 | 6 | 0 | |
| Bountiful | 274 | 0 | 0 | |
| Jenner | 271 | 5 | 2 | TTHM |
| Farmington | 270 | 3 | 0 | |
| Kenwood | 266 | 1 | 0 | |
| Warner Springs | 265 | 12 | 0 | |
| Artois | 254 | 1 | 0 | |
| Manchester | 254 | 3 | 1 | Stage 2 DBP |
| Korbel | 250 | 0 | 0 | |
| Applegate | 250 | 5 | 2 | TTHM, Total Haloacetic Acids (HAA5) |
| Colfax | 250 | 3 | 0 | |
| West Hollyhood | 250 | 7 | 1 | Stage 2 DBP |
| Billings | 244 | 4 | 1 | Stage 2 DBP |
| Fulton | 243 | 6 | 0 | |
| Shoshone | 242 | 17 | 3 | E. coli, Stage 2 DBP |
| Camptonville | 240 | 8 | 0 | |
| Ballico | 238 | 2 | 2 | E. coli |
| Casitas Springs | 238 | 5 | 1 | Stage 2 DBP |
| Paskenta | 237 | 51 | 47 | E. coli, Fecal Coliform |
| Casmalia | 234 | 7 | 0 | |
| Prunedale | 225 | 23 | 21 | Selenium, Stage 2 DBP |
| Camas | 223 | 12 | 1 | Stage 2 DBP |
| Forest Ranch | 217 | 19 | 3 | Gross Alpha, Stage 2 DBP |
| Elk Creek | 212 | 20 | 4 | Gross Alpha |
| Cherry Valley | 210 | 34 | 0 | |
| Rancho Mission Viejo | 210 | 14 | 3 | Selenium |
| Newberry Springs | 210 | 150 | 134 | Barium, Lead |
| Denver | 208 | 3 | 0 | |
| Los Altos | 200 | 6 | 0 | |
| Sierraville | 200 | 0 | 0 | |
| Bedford | 200 | 3 | 0 | |
| Romoland | 198 | 43 | 31 | E. coli, Haloacetic Acids |
| Soulsbyville | 195 | 7 | 1 | Stage 2 DBP |
| Bonita | 193 | 39 | 0 | |
| Yermo | 186 | 4 | 0 | |
| Moraga | 185 | 47 | 36 | Barium, Stage 2 DBP |
| Alderpoint | 185 | 38 | 16 | E. coli, Fecal Coliform |
| Dana Point | 185 | 41 | 0 | |
| Calpine | 182 | 32 | 32 | Barium |
| Prescott | 181 | 1 | 1 | Contaminant 1002 |
| Loma Mar | 179 | 19 | 6 | E. coli, Fecal Coliform, TTHM |
| El Dorado Hills | 178 | 7 | 4 | Gross Alpha |
| Courtland | 177 | 12 | 5 | Barium, Gross Alpha |
| Markleeville | 175 | 3 | 0 | |
| Ocotillo | 175 | 71 | 1 | Stage 2 DBP |
| Lewiston | 173 | 11 | 2 | Fecal Coliform, Stage 2 DBP |
| Knights Ferry | 168 | 6 | 6 | TTHM |
| Elverta | 166 | 11 | 11 | Selenium |
| Alpine | 165 | 54 | 26 | Haloacetic Acids, Nitrate-Nitrite, Selenium +1 more |
| Badger | 163 | 3 | 2 | E. coli |
| Auberry | 160 | 6 | 0 | |
| San Ramon | 160 | 69 | 49 | Haloacetic Acids, Nitrate-Nitrite, Selenium +1 more |
| Freedom | 160 | 12 | 0 | |
| Oregon House | 160 | 2 | 1 | Stage 2 DBP |
| Silverdale | 158 | 4 | 1 | Stage 2 DBP |
| San Mateo | 157 | 15 | 7 | Selenium, Stage 2 DBP |
| Tuolumne | 154 | 1 | 0 | |
| Acampo | 153 | 0 | 0 | |
| Richardson Springs | 150 | 2 | 0 | |
| Kyburz | 150 | 133 | 23 | E. coli |
| Toms Place | 150 | 6 | 0 | |
| Danville | 150 | 7 | 0 | |
| Corralitos | 141 | 7 | 2 | Gross Alpha |
| Bethel Island Rd | 140 | 1 | 0 | |
| San Ysabel | 140 | 7 | 0 | |
| Dunnigan | 140 | 239 | 0 | |
| Hopewell | 135 | 13 | 2 | Gross Alpha, Stage 2 DBP |
| Gaviota | 135 | 3 | 0 | |
| Plumas Lake | 135 | 4 | 2 | E. coli, Stage 2 DBP |
| Lockwood | 133 | 6 | 0 | |
| Cassel | 131 | 0 | 0 | |
| Greeley Hill | 130 | 12 | 5 | Contaminant 1028, Contaminant 1032, Stage 2 DBP |
| Emigrant Gap | 125 | 0 | 0 | |
| Agua Dulce | 124 | 25 | 20 | Barium, Combined Radium, Lead +2 more |
| Henderson | 124 | 7 | 1 | Stage 2 DBP |
| Rancho Sante Fe | 120 | 39 | 3 | Gross Alpha |
| Canby | 116 | 0 | 0 | |
| Graton | 115 | 2 | 0 | |
| Burnt Ranch | 115 | 6 | 2 | Fecal Coliform |
| Columbia | 115 | 1 | 0 | |
| Lake Hughes | 113 | 51 | 42 | Barium, Stage 2 DBP |
| Floriston | 110 | 10 | 1 | Fecal Coliform |
| Halcyon | 110 | 49 | 1 | Stage 2 DBP |
| Mt. Hamilton | 110 | 4 | 4 | Gross Alpha |
| Bell Canyon | 109 | 6 | 3 | Selenium |
| Lemon Cove | 109 | 52 | 50 | Selenium, Stage 2 DBP |
| Helm | 105 | 2 | 1 | Stage 2 DBP |
| Lake Oswego | 104 | 6 | 1 | Total Haloacetic Acids (HAA5) |
| San Marino | 104 | 8 | 0 | |
| Volcano | 103 | 2 | 0 | |
| Fiddletown | 100 | 13 | 3 | E. coli |
| Glennville | 100 | 1 | 0 | |
| Boonville | 100 | 1 | 0 | |
| Mt Laguna | 100 | 8 | 0 | |
| Guatay | 100 | 64 | 54 | Haloacetic Acids |
| Honolulu | 100 | 7 | 1 | Stage 2 DBP |
Data Sources
Drinking water data from the EPA Safe Drinking Water Information System (SDWIS). Only active community water systems (CWS) serving 100+ people are included.