| AQUARION-EASTERN FAIRFIELD COUNTY | 351,756 | 585 | Detected |
| AQUARION-STAMFORD | 119,214 | 136 | Detected |
| DANBURY WATER DEPARTMENT | 62,055 | 326 | Detected |
| AQUARION-GREENWICH | 53,297 | 114 | Detected |
| SOUTH NORWALK ELECTRIC & WATER | 42,000 | 215 | Clean |
| NORWALK FIRST TAXING DISTRICT | 40,256 | 6 | Detected |
| AQUARION-DARIEN | 18,737 | 8 | Detected |
| AQUARION-NEW MILFORD REGIONAL | 13,331 | 126 | Detected |
| AQUARION-NEW CANAAN | 10,097 | 30 | Detected |
| BETHEL WATER DEPT | 9,507 | 248 | Detected |
| AQUARION-RIDGEFIELD | 7,476 | 93 | Detected |
| AQUARION-NEWTOWN REGIONAL | 6,054 | 38 | Detected |
| FAIRFIELD HILLS | 2,610 | 64 | — |
| WESTON SCHOOLS AND MUNICIPAL BUILDINGS | 2,600 | 493 | — |
| RIDGEFIELD HIGH AND MIDDLE SCHOOL | 2,575 | 100 | — |
| NEW FAIRFIELD HIGH/MIDDLE SCHOOL | 1,791 | 576 | — |
| CONSOLIDATED & MEETING HOUSE HILL SCHOOL | 1,425 | 294 | — |
| CANDLEWOOD SHORES TAX DISTRICT | 1,315 | 382 | — |
| BROOKFIELD HIGH SCHOOL | 995 | 53 | — |
| AQUARION-RIDGEFIELD KNOLLS | 958 | 228 | — |
| WHISCONIER MIDDLE SCHOOL | 950 | 142 | — |
| JOEL BARLOW REGIONAL HIGH SCHOOL | 890 | 139 | — |
| REDDING ELEMENTARY SCHOOL | 811 | 55 | — |
| GREENWICH AMERICAN CENTER | 800 | 288 | Clean |
| LAKE WAUBEEKA ASSOCIATION | 712 | 202 | — |
| AQUARION-BALL POND | 629 | 86 | — |
| BRUNSWICK SCHOOL (LOWER & LOWER MIDDLE) | 567 | 85 | — |
| CANDLEWOOD KNOLLS WATER AUTHORITY | 524 | 478 | — |
| HEAD O MEADOW ELEMENTARY SCHOOL | 506 | 286 | — |
| STONE BRIDGE CENTER FOR HEALTH & REHAB | 504 | 303 | — |
| ST LUKES SCHOOL ATHLETIC CENTER | 500 | 17 | — |
| BRANCHVILLE SCHOOL | 488 | 6 | — |
| FAIRVIEW COUNTRY CLUB | 435 | 164 | — |
| JOHN READ MIDDLE SCHOOL | 430 | 101 | — |
| SHERMAN ELEMENTARY SCHOOL | 430 | 79 | — |
| FARMINGVILLE ELEMENTARY SCHOOL | 428 | 0 | — |
| ASPETUCK VALLEY COUNTRY CLUB-CLUBHOUSE | 415 | 10 | — |
| AQUARION-NEW FAIRFIELD | 406 | 114 | — |
| ST LUKES SCHOOL | 405 | 248 | — |
| NORDAN LLC | 400 | 14 | — |
| STONY HILL VILLAGE CONDOMINIUM ASSN | 392 | 456 | — |
| AQUA VISTA ASSOC, INC | 388 | 137 | — |
| CHURCH OF LATTER DAY SAINTS | 373 | 6 | — |
| INDIAN WELL S.P./SOUTH WELL | 367 | 32 | — |
| KNOLLCREST TAX DISTRICT | 356 | 163 | — |
| WHITBY SCHOOL | 350 | 633 | — |
| AQUARION-TIMBER TRAILS | 310 | 44 | — |
| AQUARION-POSSUM RIDGE | 307 | 244 | — |
| ARROWHEAD POINT HOMEOWNERS ASSN INC. | 296 | 53 | — |
| BRUNSWICK SCHOOL (UPPER MIDDLE) | 295 | 34 | — |