Water Quality by County
3,254 counties with public water systems.
| County | State | Systems | Population | Violations |
|---|---|---|---|---|
| Menard | Illinois | 13 | 12,238 | 423 |
| Potter | Pennsylvania | 45 | 12,233 | 15,729 |
| Jefferson | Georgia | 8 | 12,196 | 429 |
| Lyon | Iowa | 12 | 12,191 | 961 |
| Dimmit | Texas | 13 | 12,187 | 2,202 |
| Kewaunee | Wisconsin | 72 | 12,146 | 1,705 |
| Wright | Iowa | 22 | 12,136 | 927 |
| Sierra | California | 33 | 12,084 | 752 |
| Morgan | Tennessee | 1 | 12,074 | 80 |
| Lamb | Texas | 12 | 12,062 | 986 |
| Jackson | Kansas | 12 | 12,049 | 631 |
| Hancock | Illinois | 13 | 12,028 | 1,139 |
| Grant | West Virginia | 9 | 12,021 | 890 |
| Grand Isle | Vermont | 26 | 12,008 | 2,478 |
| Madison | Florida | 17 | 11,997 | 1,265 |
| Carroll | Indiana | 40 | 11,994 | 2,643 |
| Magoffin | Kentucky | 2 | 11,954 | 362 |
| County 06006 | 06 | 7 | 11,935 | 386 |
| Clay | Alabama | 5 | 11,910 | 406 |
| Aitkin | Minnesota | 124 | 11,902 | 730 |
| Baker | Florida | 19 | 11,896 | 579 |
| County 06031 | 06 | 1 | 11,888 | 21 |
| Montgomery | Missouri | 22 | 11,865 | 2,739 |
| Hampton | South Carolina | 17 | 11,858 | 286 |
| Big Horn | Wyoming | 28 | 11,830 | 799 |
| Piscataquis | Maine | 42 | 11,828 | 3,182 |
| Moffat | Colorado | 16 | 11,815 | 1,008 |
| Bradley | Arkansas | 7 | 11,749 | 272 |
| Greene | Virginia | 12 | 11,719 | 1,161 |
| Marion | Texas | 14 | 11,716 | 580 |
| Prowers | Colorado | 10 | 11,670 | 5,220 |
| Stone | Arkansas | 10 | 11,650 | 323 |
| Gates | North Carolina | 2 | 11,646 | 58 |
| Little River | Arkansas | 12 | 11,613 | 993 |
| Sierra | New Mexico | 22 | 11,599 | 1,962 |
| Barnwell | South Carolina | 19 | 11,598 | 167 |
| Jefferson | Iowa | 8 | 11,505 | 262 |
| Burke | Georgia | 24 | 11,503 | 646 |
| Boundary | Idaho | 20 | 11,485 | 1,933 |
| Johnson | Tennessee | 7 | 11,467 | 832 |
| Dodge | Georgia | 7 | 11,466 | 235 |
| Noxubee | Mississippi | 9 | 11,464 | 3,755 |
| Cherokee | North Carolina | 17 | 11,445 | 2,553 |
| Morris | Texas | 5 | 11,438 | 549 |
| Cannon | Tennessee | 1 | 11,434 | 184 |
| Noble | Ohio | 6 | 11,421 | 584 |
| Lake | Minnesota | 94 | 11,408 | 1,326 |
| Fountain | Indiana | 17 | 11,407 | 1,583 |
| Redwood | Minnesota | 30 | 11,372 | 363 |
| Pend Oreille | Washington | 44 | 11,365 | 1,579 |
| Pemiscot | Missouri | 6 | 11,341 | 490 |
| Naranjito Municipio | Puerto Rico | 6 | 11,322 | 2,411 |
| County 09007 | 09 | 17 | 11,319 | 4,099 |
| Rockbridge | Virginia | 32 | 11,317 | 895 |
| Pushmataha | Oklahoma | 8 | 11,307 | 3,856 |
| Montgomery | Iowa | 5 | 11,256 | 787 |
| Banks | Georgia | 7 | 11,249 | 223 |
| Choctaw | Oklahoma | 10 | 11,249 | 3,758 |
| Giles | Virginia | 26 | 11,239 | 3,262 |
| Renville | Minnesota | 28 | 11,220 | 416 |
| Amite | Mississippi | 10 | 11,211 | 1,954 |
| O'Brien | Iowa | 7 | 11,176 | 299 |
| Cameron Parish | Louisiana | 8 | 11,175 | 842 |
| Fergus | Montana | 20 | 11,162 | 4,498 |
| Madison | North Carolina | 42 | 11,145 | 3,104 |
| Rush | Indiana | 27 | 11,124 | 2,203 |
| Lafayette | Wisconsin | 40 | 11,118 | 1,291 |
| Ford | Illinois | 16 | 11,114 | 937 |
| Mercer | Illinois | 27 | 11,108 | 2,138 |
| Blanco | Texas | 26 | 11,106 | 2,150 |
| Washington | North Carolina | 7 | 11,093 | 686 |
| Macon | Georgia | 10 | 11,070 | 389 |
| Wilkinson | Mississippi | 9 | 11,069 | 3,229 |
| Braxton | West Virginia | 7 | 11,040 | 2,199 |
| Faribault | Minnesota | 28 | 11,026 | 212 |
| Richland | Illinois | 10 | 11,021 | 1,242 |
| Franklin | Idaho | 22 | 11,019 | 2,401 |
| Zavala | Texas | 4 | 11,003 | 818 |
| Atoka | Oklahoma | 8 | 10,995 | 3,045 |
| Chicot | Arkansas | 7 | 10,989 | 531 |
| Live Oak | Texas | 13 | 10,972 | 1,659 |
| Newton | Texas | 9 | 10,964 | 803 |
| Jones | North Carolina | 3 | 10,957 | 208 |
| Cass | Iowa | 14 | 10,945 | 1,028 |
| Bledsoe | Tennessee | 3 | 10,930 | 575 |
| Aleutians West Census Area | Alaska | 8 | 10,909 | 6,431 |
| Richland | Wisconsin | 38 | 10,908 | 1,354 |
| Kossuth | Iowa | 27 | 10,881 | 1,408 |
| Greene | Mississippi | 7 | 10,871 | 3,556 |
| Comanche | Texas | 6 | 10,854 | 825 |
| Greensville | Virginia | 7 | 10,805 | 88 |
| Cross | Arkansas | 6 | 10,768 | 354 |
| Glacier | Montana | 27 | 10,757 | 3,989 |
| Fulton | Indiana | 33 | 10,750 | 1,636 |
| County 09097 | 09 | 2 | 10,727 | 3 |
| Brunswick | Virginia | 23 | 10,720 | 816 |
| Cherry | Nebraska | 18 | 10,718 | 797 |
| Jackson | Tennessee | 5 | 10,710 | 358 |
| Mercer | North Dakota | 10 | 10,695 | 205 |
| Linn | Kansas | 12 | 10,692 | 2,238 |