| Sprague Water & Sewer Authority | Baltic, CT | 1,058 | 192 | - |
| Strawberry Park | Salt Springs, CT | 1,047 | 65 | - |
| Brookfield High School | Brookfield, CT | 995 | 53 | - |
| Aquarion-Ridgefield Knolls | Shelton, CT | 958 | 228 | - |
| Whisconier Middle School | Brookfield, CT | 950 | 142 | - |
| St. Bernard School | Uncasville, CT | 950 | 70 | - |
| Aquarion-Norfolk | Shelton, CT | 913 | 19 | - |
| Woodlake Tax District | Woodbury, CT | 912 | 63 | - |
| Ctwc - Amston Lake Division | Clinton, CT | 910 | 304 | - |
| Frito-Lay | Dayville, CT | 903 | 41 | - |
| Joel Barlow Regional High School | Easton, CT | 890 | 139 | - |
| Nonnewaug High School | Woodbury, CT | 887 | 52 | - |
| Oakdale Heights Association, Inc | Gales Ferry, CT | 876 | 67 | - |
| Kenmont & Kenwood Camps | South Kent, CT | 825 | 21 | - |
| Aquarion-Kent | Shelton, CT | 817 | 22 | - |
| Southbury Training School | Southbury, CT | 816 | 370 | - |
| Redding Elementary School | Easton, CT | 811 | 55 | - |
| Haddam Killingworth Inter/Middle School | Killingworth, CT | 808 | 308 | - |
| Sharon Water & Sewer Commission | Sharon, CT | 803 | 309 | - |
| Greenwich American Center | Greenwich, CT | 800 | 288 | Clean |
| Hopeville Pond S.p./Beach-Well #2 | Portland, CT | 800 | 22 | - |
| Horace Porter School | Columbia, CT | 797 | 100 | - |
| Talcott Mountain S.p. | Portland, CT | 793 | 22 | - |
| Haddam Meadows S.p. | Portland, CT | 780 | 50 | - |
| Shepaug Middle/High School | Washington, CT | 770 | 42 | - |
| Bolton Center School (K-8) | Bolton, CT | 756 | 59 | - |
| Housatonic Valley Regional Hs | Falls Village, CT | 750 | 97 | - |
| Ctwc - Jensens Beechwood System | Clinton, CT | 750 | 447 | - |
| Ctwc - Uconn South Eagleville Div. | Clinton, CT | 750 | 0 | - |
| Clc Owners Corporation | Brookfield, CT | 736 | 454 | - |
| Kent School Corp (Valley Campus) | Kent, CT | 722 | 190 | - |
| Lake Garda School | Burlington, CT | 715 | 27 | - |
| Mansfield Middle School | Mansfield, CT | 715 | 38 | - |
| Lake Waubeeka Association | Danbury, CT | 712 | 202 | - |
| Ctwc - Spice Hill Division | Clinton, CT | 712 | 210 | - |
| Penwood State Park/Main Park Well | Portland, CT | 700 | 13 | - |
| Ctwc - Coventry Hills Div | Clinton, CT | 700 | 27 | Clean |
| Mansfield Elementary School | Mansfield, CT | 688 | 30 | - |
| Indian Field Coop Campground Assn., Inc. | Salem, CT | 685 | 223 | - |
| Salem Elementary School | Salem, CT | 675 | 93 | - |
| YMCA Camp Ingersoll | Middletown, CT | 653 | 5 | - |
| Scwa, Ledyard Center Division | Gales Ferry, CT | 652 | 43 | - |
| Ctwc - Lake Hayward | Clinton, CT | 650 | 86 | - |
| Haddam-Killingworth High School | Killingworth, CT | 642 | 85 | - |
| Alcott School | Wolcott, CT | 638 | 108 | - |
| Woodstock Elementary School | Woodstock, CT | 636 | 13 | - |
| Aquarion-Ball Pond | Shelton, CT | 629 | 86 | - |
| Nathan Hale-Ray Middle School | Moodus, CT | 620 | 7 | - |
| Lisbon Central School | Lisbon, CT | 620 | 41 | - |
| Woodstock Academy South Campus | Woodstock, CT | 620 | 158 | - |