We found 14 public water systems in DeKalb county (ordered by population size).
| Name | Areas served | Population served | Contaminant count | Violation count |
|---|---|---|---|---|
| Mo American St Joseph | Andrew, Dekalb, Elwood, Ks, St. Joseph, Wathena | 71,000 | 20 | 0 |
| Dekalb Co Pwsd 1 | Clarksdale | 7,070 | 0 | 3 |
| Clinton Co Pwsd 3 | Counties of Caldwell, Clinton, Daviess, Dekalb | 3,410 | 0 | 9 |
| Maysville | Maysville | 1,104 | 0 | 93 |
| Stewartsville | Stewartsville | 750 | 0 | 6 |
| Osborn | Osborn | 450 | 0 | 14 |
| Pony Express Wildlife Area | Osborn | 450 | 0 | 0 |
| Union Star | County of Dekalb | 437 | 0 | 8 |
| Clarksdale | Clarksdale | 271 | 0 | 2 |
| Pony Express Package Store | Pony Express | 100 | 0 | 0 |
| Fairport Baptist Church | Fairport Baptis | 25 | 0 | 0 |
| Montrose Wildlife Area | Montrose | 25 | 0 | 0 |
| Proud Marys Roadhouse | Proud Marys | 25 | 0 | 0 |
| Presbyterian Church | Presbyterian | 25 | 0 | 0 |