| INDIANA AMERICAN WATER - NORTHWEST | 210,510 | 15 | Clean |
| HAMMOND WATER WORKS DEPARTMENT | 78,384 | 38 | Clean |
| CROWN POINT WATER WORKS | 30,000 | 27 | Clean |
| SCHERERVILLE WATER DEPARTMENT | 30,000 | 23 | Clean |
| EAST CHICAGO WATER WORKS | 26,370 | 148 | Clean |
| ST. JOHN MUNICIPAL WATER UTILITY | 25,700 | 100 | Detected |
| HIGHLAND WATER WORKS | 23,984 | 23 | Clean |
| MUNSTER WATER COMPANY | 23,894 | 35 | Clean |
| GRIFFITH WATER DEPARTMENT | 16,893 | 19 | Clean |
| DYER WATER DEPARTMENT | 16,800 | 12 | Clean |
| INDIANA AMERICAN WATER - LOWELL | 11,908 | 292 | Detected |
| CUII - TWIN LAKES | 8,000 | 62 | Detected |
| NEW CHICAGO WATER WORKS | 5,500 | 31 | Clean |
| WHITING WATER DEPARTMENT | 4,900 | 65 | Clean |
| CEDAR LAKE WATER WORKS | 4,600 | 465 | Detected |
| CUII - INDIANA WATER SERVICE | 4,200 | 34 | Clean |
| PILOT/WENDYS #448 | 2,435 | 312 | — |
| FLYING J #653 | 1,450 | 387 | — |
| LOWELL COMMONS | 1,440 | 31 | — |
| AQUA INDIANA WATER COMPANY | 1,350 | 6 | — |
| CEDAR LAKE - ROBINS NEST | 950 | 136 | — |
| APPLE VALLEY UTILITIES, INC. | 712 | 182 | Detected |
| LUKE OIL #293 | 606 | 168 | — |
| WINFIELD ELEMENTARY SCHOOL | 546 | 66 | — |
| LAKE PRAIRIE ELEMENTARY | 540 | 82 | — |
| LITTLE CALUMET RIVER BASIN-ARTESIAN WELL | 500 | 9 | — |
| BETHEL CHURCH CEDAR LAKE | 473 | 21 | — |
| DYER INDOOR SOCCER ARENA | 302 | 17 | — |
| LIGHTHOUSE RESTAURANT AT PARADISE COVE | 275 | 34 | — |
| SCHNEIDER WATER DEPARTMENT | 267 | 124 | — |
| LAKESHORE SUBDIVISION ASSOCIATION, INC. | 265 | 509 | — |
| HARRY OS | 220 | 102 | — |
| FAIRWAY REGIONAL WATER DISTRICT | 210 | 192 | — |
| ST. MICHAEL THE ARCHANGEL CHURCH | 200 | 3 | — |
| CEDAR LAKE MOBILE HOME PARK | 200 | 1,082 | — |
| NORTHWEST INDIANA ISLAMIC CENTER | 199 | 18 | — |
| HILLSIDE COMMUNITY CHURCH | 190 | 92 | — |
| BOYS AND GIRLS CLUBS OF NW IN-CEDAR LAKE | 160 | 156 | — |
| PROTECTION OF THE VIRGIN MARY ORTH CH | 150 | 13 | — |
| HANOVER NORTH PROFESSIONAL BUILDING | 150 | 16 | — |
| CEDAR LAKE BIBLE CONFERENCE GROUNDS | 150 | 222 | — |
| GRACE EVANGELICAL LUTHERAN CHURCH | 140 | 4 | — |
| SUBWAY/R.A.K. HOLDINGS LLC | 129 | 15 | — |
| PALMIRA GOLF & COUNTRY CLUB | 129 | 105 | — |
| HOLY NAME CH./GRAND TOTS DAYCARE | 115 | 25 | — |
| TOWN OF CEDAR LAKE - COMPLEX & PUMPHOUSE | 115 | 78 | — |
| ROSS BAPTIST CHURCH | 110 | 54 | — |
| INDIAN RIDGE GOLF COURSE | 106 | 112 | — |
| THE SANDBAR GRILL | 104 | 372 | — |
| TASTEE TOP | 104 | 40 | — |