PFAS in tap water, Chester County, Pennsylvania
6 of 11 water systems had PFAS-4 above our 0.5 ng/L benchmark at the latest sample. Highest: PA American Royersford, 24.8 ng/L. 9 had PFOA or PFOS above the 4 ng/L federal MCL in at least one sample.
11 community water systems · 230,414 people served · newest sample December 17, 2025
Water systems in Chester County
| Water system | People served | PFAS-4 at the latest sample | Entry points | Latest sample |
|---|---|---|---|---|
| PA American Royersford | 49,508 | 24.8 ng/L above the 2029 federal MCL | 5 | October 8, 2024 |
| Aqua PA West Chester | 48,600 | below the 3 to 4 ng/L reporting limit above the 2029 federal MCL in an earlier sample | 2 | October 10, 2024 |
| PA American Coatesville | 36,960 | below the 3 to 4 ng/L reporting limit | 1 | February 3, 2025 |
| Aqua PA Uwchlan | 35,518 | 13 ng/L above the 2029 federal MCL | 7 | October 25, 2024 |
| Phoenixville Water Dept | 16,599 | 4.9 ng/L above the 2029 federal MCL | 1 | November 25, 2024 |
| Downingtown Water Authority | 9,900 | below the 3 to 4 ng/L reporting limit above the 2029 federal MCL in an earlier sample | 1 | October 15, 2024 |
| Aqua PA Friendship | 8,800 | 19.3 ng/L above the 2029 federal MCL | 7 | October 16, 2024 |
| Aqua PA Spring Run | 8,151 | 14.4 ng/L above the 2029 federal MCL | 4 | October 15, 2024 |
| Kennett Square Mun Water Works | 6,328 | below the 3 to 4 ng/L reporting limit above the 2029 federal MCL in an earlier sample | 3 | January 29, 2024 |
| Oxford Borough | 5,280 | 4.3 ng/L above the 2029 federal MCL | 2 | December 17, 2025 |
| London Grove TWP Mun Auth | 4,770 | below the 3 to 4 ng/L reporting limit | 2 | October 14, 2024 |
Not sure which one is yours? The systems report their own service areas to EPA. Check your water bill or your utility's Consumer Confidence Report.
ZIP codes in Chester County
Census ZIP code tabulation areas that overlap the county. A ZIP served by one system opens that system's page; a ZIP shared by several systems lists them.
How to read these numbers
We compare PFAS-4 (PFOA + PFOS + PFNA + PFHxS) with this site's 0.5 ng/L benchmark, the same line as on the European pages. UCMR 5 reporting limits are 3 to 4 ng/L. So any quantified PFAS-4 compound is above the benchmark, and a clean result reads "below the 3 to 4 ng/L reporting limit", never zero. The US legal limit is the 4 ng/L federal MCL for PFOA and PFOS, which systems must meet from April 26, 2029 ("above the 2029 federal MCL").
EPA: "UCMR 5 results do not indicate compliance or noncompliance with the PFAS drinking water standards". Samples are taken where water enters the distribution system, not at your tap. A system may have changed sources or added treatment since. Source: U.S. Environmental Protection Agency (EPA), Office of Water, PFAS National Primary Drinking Water Regulation (NPDWR). Regulation details retrieved September 19, 2026. Every system page tracks the 2029 compliance date and the proposed rescission of the PFHxS, PFNA, HFPO-DA and Hazard Index limits.
This site is a data project, not an official source. If in doubt, check with your water supplier or local authority.