| CITY OF LAKE CHARLES WATER SYSTEM | 79,500 | 15 | Detected |
| SULPHUR CITY OF WATER SYSTEM | 24,489 | 71 | Detected |
| CALCASIEU PARISH WW DISTRICT NO 1 | 20,837 | 30 | Detected |
| CALCASIEU PARISH WW DIST 9 CARLYSS | 14,502 | 56 | Detected |
| HOUSTON RIVER WATERWORKS DISTRICT 11 | 6,915 | 33 | Detected |
| CALCASIEU PARISH WW DISTRICT 8 | 6,834 | 19 | Detected |
| CALCASIEU PARISH WW DISTRICT NO 5 | 5,388 | 37 | Detected |
| DEQUINCY WATER SYSTEM (LAWCO) | 5,370 | 1 | Detected |
| CALCASIEU PARISH WW DISTRICT NO 4 | 5,340 | 28 | Detected |
| WESTLAKE CITY OF WATER SYSTEM | 4,858 | 57 | Detected |
| CALCASIEU PARISH WW DISTRICT 7 | 4,791 | 15 | Clean |
| TOWN OF VINTON WATER SYSTEM | 4,101 | 16 | Detected |
| TOWN OF IOWA WATER SYSTEM | 3,636 | 39 | Detected |
| CALCASIEU WW #14 WARD 5 | 3,150 | 47 | — |
| DELTA DOWNS INC WATER SYSTEM | 2,481 | 39 | — |
| GULF STREAM MANOR WATER SYSTEM | 2,130 | 210 | — |
| CALCASIEU PARISH WW 12 WARD 3 | 2,130 | 4 | — |
| WESTLAKE US 2 LLC S COMPLEX WATER SYSTEM | 1,700 | 33 | — |
| CITGO PETROLEUM REFINERY WATER SYSTEM | 1,263 | 65 | — |
| QUAIL RIDGE ESTATES WATER SYSTEM | 1,119 | 25 | — |
| TOOMEY REST AREA WATER SYSTEM | 1,001 | 1 | — |
| WATERWORKS DIST. NO. 10 OF WARD 7 | 942 | 9 | — |
| COUNTRY PINES NORTH SUBDIVISION WS | 936 | 100 | — |
| PHILLIPS 66 LAKE CHARLES REFINERY | 770 | 53 | — |
| FAIRVIEW MOBILE ESTATES NORTH WS | 669 | 20 | — |
| MOSSVILLE WW DISTRICT NO 2 | 660 | 47 | — |
| MAGNOLIA-LAKE STREET | 651 | 61 | — |
| MAPLEWOOD PLACE PARK WATER SYSTEM | 597 | 1 | — |
| COUNTRY PINES SOUTH SUBDIVISION WS | 570 | 0 | — |
| THE CHARLESTON MHC WATER SYSTEM | 567 | 40 | — |
| BORDER TOWN TRAVEL PLAZA | 500 | 1 | — |
| GARDEN HEIGHTS WATER SYSTEM | 465 | 13 | — |
| SMITH MOBILE HOME VILLAGE WATER SYSTEM | 444 | 97 | — |
| THE SALLIER MHC WATER SYSTEM | 400 | 44 | — |
| FAIRVIEW MOBILE ESTATES SOUTH WS | 378 | 26 | — |
| PRAIRIE PLAZA WATER SYSTEM | 350 | 45 | — |
| OAK MEADOWS SUBDIVISION WATER SYSTEM | 318 | 35 | — |
| MAGNOLIA-UTILITY SERVICE OF LAKE CHARLES | 306 | 106 | — |
| THE LONGHORN TRUCK STOP AND RESTAURANT | 300 | 4 | — |
| CASH MAGIC-VINTON WATER SYSTEM | 300 | 8 | — |
| LAKE CHARLES HARBOR TERMINAL DISTRICT WS | 300 | 0 | — |
| MAGNOLIA-BRIGAS ESTATES | 294 | 128 | — |
| SUGARCANE TOWNES WATER SYSTEM | 288 | 6 | — |
| OSPREY LAKES RV PARK WATER SYSTEM | 279 | 12 | — |
| OAK PINE MOBILE HOME PARK WATER SYSTEM | 240 | 66 | — |
| PHAROS MOBILE HOME COMMUNITY SOUTH | 222 | 132 | — |
| RIVER CHURCH WATER SYSTEM | 220 | 15 | — |
| TEXAS PELICAN COMPLEX | 200 | 28 | — |
| PHAROS MOBILE HOME COMMUNITY NORTH | 162 | 143 | — |
| THE RESERVE MHC WATER SYSTEM | 159 | 30 | — |