County · Illinois
St. Clair County, Illinois: drinking water records
This overview covers 27 ZIP codes and 24 community water systems in St. Clair County. It also stands in for 0 ZIP codes whose utility has too little EPA data for a page of its own.
System population figures are summed from EPA registry records and can overlap where wholesalers and retail systems serve the same people. They are not a Census county-population estimate.
Water systems with the most complete records
| Water system | People served | PFAS survey results | PFAS found | Health-based violations | Lead, 9 in 10 homes at or below |
|---|---|---|---|---|---|
| Il American-East St Louis IL1635040 | 131,368 | 120 | 3 | 0 | 3 ppb |
| O Fallon IL1631100 | 46,603 | 120 | 1 | 0 | 2.2 ppb |
| Caseyville IL1630250 | 13,798 | 120 | 1 | 0 | 0 ppb |
| Cahokia Heights IL1635000 | 12,528 | 120 | 3 | 0 | 0 ppb |
| Mascoutah IL1630800 | 8,759 | 120 | 0 | 0 | 6 ppb |
| American Water Oper and Maintenance, LLC IL1635237 | 6,779 | 120 | 2 | 0 | 6 ppb |
| Lebanon IL1630650 | 4,714 | 120 | 0 | 0 | 12.2 ppb |
| Freeburg IL1630600 | 4,707 | 240 | 1 | 0 | 5.6 ppb |
| Dupo IL1630350 | 4,684 | 60 | 3 | 0 | 0 ppb |
| Millstadt IL1630850 | 4,071 | 120 | 4 | 0 | 0 ppb |
| New Athens IL1631050 | 1,970 | 0 | 0 | 1 | 5.2 ppb |
| Marissa IL1630750 | 1,921 | 0 | 0 | 1 | 2.3 ppb |
| Mound Pwd IL1635050 | 1,500 | 0 | 0 | 1 | 0 ppb |
| Lenzburg IL1630700 | 616 | 0 | 0 | 1 | 0 ppb |
| Fsh Water Commission IL1635300 | 313 | 0 | 0 | 1 | 5 ppb |
| Smithton IL1631300 | 4,381 | 0 | 0 | 0 | 0 ppb |
| Prairie Dupont Pwd IL1635070 | 1,863 | 0 | 0 | 0 | 0 ppb |
| St Libory IL1631200 | 628 | 0 | 0 | 0 | 0 ppb |
| Fayetteville IL1630550 | 490 | 0 | 0 | 0 | 0 ppb |
| S L M Water Commission IL1635090 | 385 | 0 | 0 | 0 | 3.6 ppb |
| Arapaho Village MHP IL1635055 | 368 | 0 | 0 | 0 | 0 ppb |
| Summerfield IL1631350 | 347 | 0 | 0 | 0 | 3.4 ppb |
| Kaskaskia Water District IL1635110 | 0 | 0 | 0 | 1 | not reported |
| Southwestern Il Correctional Center IL1630030 | 563 | 0 | 0 | 0 | not reported |
ZIP reports in St. Clair County
No ZIP report in this county is published yet.
Sources and scope
EPA UCMR 5 occurrence data, samples collected 2023-01-03 – 2026-06-17, final release, August 2026 (file dated Aug 28, 2026); EPA SDWIS via ECHO, 2026Q2 extract (file dated Jul 9, 2026); EPA service-area boundaries v3.0; Census 2020 ZCTAs. Page generated 2026-09-03.
Counts cover the systems that report this county to EPA. A water system may cross county lines. "Found" means at least one result at or above the laboratory reporting level; it is not a compliance finding.