| LOS ANGELES-CITY, DEPT. OF WATER & POWER | 3,875,566 | 33 | Detected |
| LONG BEACH UTILITIES DEPARTMENT | 466,772 | 6 | Detected |
| SANTA CLARITA VALLEY WATER AGENCY | 294,090 | 4 | Detected |
| GSWC - SOUTHWEST | 277,740 | 11 | Detected |
| SAN GABRIEL VALLEY WATER CO.-EL MONTE | 248,000 | 13 | Detected |
| LOS ANGELES CWWD 40 REG 4 & 34 LANCASTER | 208,129 | 11 | Detected |
| GLENDALE-CITY, WATER DEPT. | 188,784 | 2 | Detected |
| SUBURBAN WATER SYSTEMS-SAN JOSE | 168,843 | 10 | Detected |
| PASADENA WATER AND POWER | 164,344 | 8 | Detected |
| CALIFORNIA WATER SERVICE CO. - ELA | 152,474 | 13 | Detected |
| POMONA - CITY, WATER DEPT. | 151,713 | 14 | Detected |
| CALIFORNIA WATER SERVICE CO. - DOMINGUEZ | 143,996 | 19 | Detected |
| PALMDALE WATER DIST. | 126,804 | 12 | Detected |
| AZUSA LIGHT AND WATER | 110,044 | 2 | Detected |
| DOWNEY - CITY, WATER DEPT. | 108,816 | 16 | Detected |
| TORRANCE-CITY, WATER DEPT. | 106,183 | 57 | Detected |
| BURBANK-CITY, WATER DEPT. | 105,603 | 16 | Detected |
| WALNUT VALLEY WATER DISTRICT | 100,941 | 5 | Detected |
| CALIFORNIA WATER SERVICE CO. - HERM/REDO | 96,853 | 10 | Detected |
| SANTA MONICA-CITY, WATER DIVISION | 89,947 | 3 | Detected |
| INGLEWOOD- CITY, WATER DEPT. | 80,824 | 16 | Detected |
| CITY OF ALHAMBRA | 79,776 | 8 | Detected |
| SOUTH GATE-CITY, WATER DEPT. | 76,443 | 127 | Detected |
| COMPTON-CITY, WATER DEPT. | 74,877 | 20 | Detected |
| LIBERTY UTILITIES - BELLFLOWER-NORWALK | 72,624 | 4 | Detected |
| LAS VIRGENES MWD | 72,602 | 9 | Detected |
| CALIFORNIA WATER SERVICE CO. - PALOS VER | 71,452 | 6 | Detected |
| VALLEY COUNTY WATER DIST. | 68,871 | 8 | Clean |
| LYNWOOD-CITY, WATER DEPT. | 66,967 | 20 | Detected |
| LAKEWOOD - CITY, WATER DEPT. | 66,135 | 6 | Detected |
| SUBURBAN WATER SYSTEMS-WHITTIER | 66,045 | 4 | Detected |
| GSWC - FLORENCE/GRAHAM | 63,500 | 2 | Detected |
| MONTEREY PARK-CITY, WATER DEPT. | 62,183 | 9 | Detected |
| SUBURBAN WATER SYSTEMS-LA MIRADA | 56,793 | 0 | Detected |
| GSWC-SAN DIMAS | 56,538 | 5 | Detected |
| PARAMOUNT - CITY, WATER DEPT. | 55,200 | 7 | Detected |
| GSWC - BELL, BELL GARDENS | 54,877 | 8 | Detected |
| ROWLAND WATER DISTRICT | 54,660 | 4 | Detected |
| CITY OF ARCADIA | 51,361 | 17 | Detected |
| GSWC - ARTESIA | 50,375 | 5 | Detected |
| WHITTIER-CITY, WATER DEPT. | 49,954 | 0 | Clean |
| GLENDORA-CITY, WATER DEPT. | 49,934 | 4 | Clean |
| CAL/AM WATER COMPANY - SAN MARINO | 47,995 | 2 | Detected |
| CERRITOS - CITY, WATER DEPT. | 47,475 | 0 | Detected |
| BELLFLOWER - SOMERSET MWC | 46,300 | 2 | Detected |
| HAWTHORNE-CITY WATER DEPT. | 44,718 | 8 | Detected |
| GSWC - NORWALK | 43,176 | 3 | Detected |
| PICO RIVERA - CITY, WATER DEPT. | 40,600 | 17 | Detected |
| BEVERLY HILLS-CITY, WATER DEPT. | 40,121 | 91 | Detected |
| GSWC - CLAREMONT | 39,730 | 6 | Detected |