| SANTA MARGARITA RECREATION AREA | 50,001 | 0 | — |
| SAN LUIS OBISPO WATER DEPARTMENT | 47,788 | 2 | Detected |
| CITY OF PASO ROBLES WATER DIVISION | 31,176 | 9 | Detected |
| ATASCADERO MUTUAL WATER CO | 30,618 | 3 | Detected |
| CITY OF ARROYO GRANDE UTILITIES DIVISION | 17,963 | 7 | Detected |
| CALIFORNIA MENS COLONY | 15,000 | 11 | Clean |
| NIPOMO COMM SERVICES DIST | 13,771 | 8 | Detected |
| MORRO BAY PW DEPT - WATER DIVISION | 13,757 | 13 | Clean |
| CITY OF GROVER BEACH PUBLIC WORKS DEPT | 12,701 | 8 | Clean |
| BRECON ESTATE | 9,012 | 0 | — |
| PISMO BEACH WATER DEPARTMENT | 8,036 | 13 | Detected |
| TEMPLETON CSD | 8,011 | 4 | Detected |
| OCEANO COMM SERVICES DIST. | 7,601 | 23 | Clean |
| LOS OSOS COMMUNITY SERVICES DISTRICT | 7,086 | 3 | Detected |
| GOLDEN STATE WATER COMPANY - LOS OSOS | 5,924 | 0 | Detected |
| CAMBRIA COMM SERVICES DIST | 5,532 | 22 | Clean |
| GOLDEN STATE WATER COMPANY - NIPOMO | 4,506 | 0 | Detected |
| ATASCADERO STATE HOSPITAL | 4,100 | 6 | Detected |
| WOODLANDS DEVELOPMENT | 3,862 | 3 | — |
| GROSSO KRESSER WINERY | 3,606 | 0 | — |
| HERITAGE RANCH CSD | 2,956 | 38 | Clean |
| SAN MIGUEL COMMUNITY SERVICES DISTRICT | 2,600 | 2 | — |
| CAYUCOS BEACH MUTUAL WATER COMPANY | 2,567 | 1 | — |
| MORRO ROCK MUTUAL WATER CO | 2,181 | 1 | — |
| NACIMIENTO WATER COMPANY | 2,181 | 103 | — |
| GOLDEN STATE WATER COMPANY-CYPRESS RIDGE | 2,026 | 48 | — |
| AVILA BEACH COMMUNITY SERVICES DISTRICT | 1,630 | 0 | — |
| TIGER WATER SUPPLY | 1,600 | 5 | — |
| SAN MIGUELITO MWC | 1,600 | 5 | — |
| LOPEZ PROJECT | 1,569 | 5 | — |
| COUNTY OF MONTEREY-LAKE NACIMIENTO | 1,521 | 10 | — |
| GOLDEN STATE WATER COMPANY - EDNA | 1,493 | 2 | — |
| CALTRANS - SHANDON REST STOP | 1,300 | 10 | — |
| SLO CWWD NO. 23 - SANTA MARGARITA | 1,291 | 2 | — |
| PG&E | 1,200 | 26 | — |
| SLOCSA #10A - CAYUCOS | 1,200 | 0 | — |
| SLO CSA NO. 16 - SHANDON | 1,085 | 0 | — |
| DAOU VINEYARDS, LLC | 1,025 | 2 | — |
| MONTANA DE ORO STATE PARK | 990 | 7 | — |
| LAUREATE WATER COMPANY | 700 | 14 | — |
| COASTAL CHRISTIAN SCHOOL | 650 | 0 | — |
| MESA DUNES MOBILE HOME ESTATES | 600 | 15 | — |
| S & T MUTUAL WATER COMPANY | 591 | 3 | — |
| WOODLAND PARK MUTUAL WATER CO | 538 | 21 | — |
| HEARST MEMORIAL STATE BEACH | 500 | 2 | — |
| WALNUT HILLS MUTUAL WATER CO | 486 | 4 | — |
| SAN SIMEON CSD | 462 | 8 | — |
| GARDEN FARMS C.W.D. | 440 | 13 | — |
| LOS ROBLES MOBILE HOME ESTATES | 420 | 4 | — |
| VINES R.V. RESORT | 400 | 0 | — |