McHenry County tap water
1 of 12 water systems serving McHenry County with full PFAS testing averaged above a 2024 federal PFAS level at one or more sampling points.
- 32 community water systems list this county as served; 12 serve 3,300+ people with full PFAS testing.
- 4 had a health-based violation since 2021-10-26.
Largest systems serving this county
| System | Source | People served (whole system) | PFAS above a 2024 level? | Violations since 2021-10-26 |
|---|---|---|---|---|
| Crystal Lake | Groundwater | 40,661 | No | 0 |
| Algonquin | Groundwater | 30,700 | No | 0 |
| Lake in the Hills | Groundwater | 28,661 | No | 0 |
| Huntley | Groundwater | 28,495 | No | 1 |
| Woodstock | Groundwater | 25,630 | No | 1 |
| Mchenry | Groundwater | 22,335 | No | 0 |
| Cary | Groundwater | 17,826 | No | 0 |
| Harvard | Groundwater | 9,469 | No | 0 |
| IL American-Whispering Hills | Groundwater | 8,300 | Yes | 1 |
| Marengo | Groundwater | 7,572 | No | 0 |
| Fox River Grove | Groundwater | 4,702 | No | 0 |
| Wonder Lake | Groundwater | 3,870 | No | 1 |
Which one is yours? A county usually has several utilities. Your bill or your utility's annual water-quality report names yours. Population is for the whole system, which can cross county lines.
Not medical or legal advice. UCMR 5 results are screening data, not compliance determinations.
Sources and freshness
Public-water-system facts, violations and lead/copper results: EPA ECHO SDWA download (SDWIS snapshot 2026-10-13). PFAS and lithium results: EPA UCMR 5 final data (sampling 2023–2025). Both are U.S. government works, downloaded 2026-10-26. Numbers are computed by the published method; the same fields are in the open data files.