| YONKERS CITY | 211,569 | 17 | Clean |
| VEOLIA WATER NEW YORK, INC. RD-1 | 146,732 | 101 | Clean |
| MOUNT VERNON WATER DEPARTMENT | 73,893 | 5 | Clean |
| WESTCHESTER JOINT WATER WORKS | 59,629 | 66 | Clean |
| WHITE PLAINS CITY | 59,559 | 11 | Clean |
| VEOLIA WATER NEW YORK, INC. RD-2 | 57,301 | 8 | Detected |
| GREENBURGH CONSOLIDATED WD #1 | 39,993 | 28 | Clean |
| YORKTOWN CONSOLD. WATER DIST.#1 | 36,000 | 60 | Detected |
| OSSINING WATER DEPARTMENT | 30,000 | 311 | Detected |
| CORTLANDT CONSOLIDATED WD | 28,369 | 102 | Clean |
| PEEKSKILL CITY | 24,272 | 153 | Clean |
| SCARSDALE WATER DEPARTMENT | 21,649 | 0 | Clean |
| KENSICO WATER DISTRICT | 17,917 | 58 | Clean |
| NEW CASTLE/STANWOOD W.D. | 17,116 | 105 | Clean |
| MOUNT KISCO WATER DEPARTMENT | 11,187 | 46 | Detected |
| TARRYTOWN WATER SUPPLY | 11,000 | 104 | Clean |
| SLEEPY HOLLOW (VILLAGE) | 9,870 | 86 | Clean |
| PLEASANTVILLE WATER DISTRICT | 9,550 | 45 | Clean |
| BRIARCLIFF MANOR VILLAGE | 9,190 | 98 | Clean |
| BEDFORD CONSOLIDATED W.D. | 9,056 | 23 | Detected |
| CROTON ON HUDSON VILLAGE | 8,000 | 79 | Clean |
| IRVINGTON WATER SUPPLY | 6,631 | 47 | Clean |
| LARCHMONT VILLAGE | 6,485 | 18 | Clean |
| WESTCHESTER COUNTY WD #3 | 6,000 | 318 | Clean |
| ELMSFORD VILLAGE | 5,293 | 33 | Clean |
| HERITAGE HILLS WATER SYSTEM | 4,700 | 645 | Detected |
| SOMERS CONSOLIDATED WATER DISTRICT #1 | 3,848 | 0 | — |
| MONTROSE IMPROVEMENT DISTRICT | 3,100 | 28 | — |
| FOX LANE HIGH & MIDDLE SCHOOLS | 3,000 | 26 | — |
| PACE UNIVERSITY | 2,753 | 21 | — |
| NORTH CASTLE WATER DISTRICT #1 | 2,500 | 12 | — |
| BUCHANAN VILLAGE | 2,200 | 33 | — |
| OLD FARM HILL WATER DISTRICT | 1,768 | 24 | — |
| OLD POST ROAD WATER DISTRICT | 1,500 | 22 | — |
| JOHN JAY SENIOR HIGH SCHOOL | 1,425 | 154 | — |
| NORTH CASTLE WATER DISTRICT #4 | 1,225 | 60 | — |
| NORTH CASTLE WATER DISTRICT #2 | 1,200 | 47 | — |
| SOMERS HIGH SCHOOL | 1,189 | 2 | — |
| BEDFORD REST AREA NYS RT 684 | 1,000 | 30 | — |
| SAINT JOSEPH CHURCH (NEW) | 1,000 | 0 | — |
| GREENBRIAR SUBDIVISION | 956 | 596 | — |
| JOHN JAY MIDDLE SCHOOL | 945 | 188 | — |
| PRIMROSE SCHOOL | 900 | 6 | — |
| SEVEN-ELEVEN STORE | 900 | 0 | — |
| OAKRIDGE WATER DISTRICT | 892 | 102 | — |
| JOHN F KENNEDY HIGH SCHOOL | 840 | 37 | — |
| WILD OAKS WATER COMPANY | 805 | 55 | — |
| BYRAM HILLS HIGH SCHOOL | 800 | 436 | — |
| SWISS RE OF AMERICA | 800 | 224 | — |
| SOMERS MIDDLE SCHOOL | 790 | 16 | — |