We read 6 results from O Fallon’s 2025 water quality report. No results over a legal limit or above a health goal.
Serves about 46,603 people · Water system ID IL1631100 · Read the district’s 2025 report (opens in a new tab)
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Results from the 2025 report
Each number is copied from the district’s report and links to the page it’s printed on. Where the report lists several plants, wells or purchased water, the highest is shown.
| Contaminant | Result | Health goal | Legal limit | What it means |
|---|---|---|---|---|
| Chlorinehighest measured · range 2 to 3 · listed as a violation in the report · Distribution system · 2025 report, page 8 | 2.8 ppm | None set | 4 ppm | Below the legal limit |
| Copper90th percentile of homes tested, 1 over the action level · listed as a violation in the report · Customer taps · 2025 report, page 8 | 0.14 ppm | 0.3 ppm | 1.3 ppm (action level) | Below the health goal |
| Disinfection byproducts (TTHM)highest running annual average · range 34.2 to 57.4 · listed as a violation in the report · Distribution system · 2025 report, page 8 | 50 ppb | None set | 80 ppb | Below the legal limit |
| Lead90th percentile of homes tested, 1 over the action level · listed as a violation in the report · Customer taps · 2025 report, page 8 | Not detected | 0.2 ppb | 15 ppb (action level) | Not detected |
| Lithiumaverage · range ND to 11.6 · sampled 2024 · Distribution system · 2025 report, page 9 | 5.3 ppb | None set | None | No health limit |
| PFBA (a PFAS)average · range 9.9 to 13 · sampled 2024 · Distribution system · 2025 report, page 9 | 11.7 ppt | None set | None | No health limit |
Utility results describe the whole system, measured where water enters the pipes, not your tap. Your home’s plumbing can add lead or copper. 1 number we weren’t sure about is held back until a person checks.
EPA testing for PFAS and lithium
EPA’s own nationwide testing (UCMR 5) found these in O Fallon’s water between Feb 2024 and Nov 2024. These are EPA lab results, separate from the district’s report. Anything not listed was not detected.
- Lithium11.6 ppbFound in 2 of 4 samples · highest resultAbove EPA’s health reference level of 10 ppb (a guide, not a legal limit)
Source: EPA UCMR 5 occurrence data. The highest single result is shown; one high sample doesn’t mean every glass is that high.
What you can do
Nothing in this report is above a health goal or legal limit. If you’re bothered by taste, smell, hardness or spots, or your home has older pipes, the filter catalog and buyer questions can help you pick, and a test of your own tap shows what your plumbing adds.
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