Well water in Chester County, PA
What Penn State well tests show for Chester County, compared with Pennsylvania as a whole.
In short
About 29% of the Chester County well samples Penn State tested were positive for coliform bacteria (statewide: 44%). Compared with the rest of Pennsylvania, it stands out for pH outside the normal range (29% vs. 17% statewide).
What local well tests found
29%failed for coliform bacteria
83%were corrosive to plumbing
15%had manganese over the stain level
| Test (share of samples over the guideline) | Chester County | Pennsylvania |
|---|---|---|
| Total coliform bacteria | 29.3% | 44.1% |
| E. coli bacteria | 2.2% | 10.6% |
| Corrosivity (likely to eat pipes) | 83.3% | 65.9% |
| pH outside 6.5 to 8.5 | 29.2% | 16.6% |
| Manganese (stains) | 14.8% | 22.3% |
| Iron (stains) | 14.6% | 17.2% |
| Lead, first-draw sample | 9.2% | 8.9% |
| Arsenic | 1.2% | 5.5% |
| Nitrate | 5.2% | 4.1% |
| Typical hardness (median) | 4.8 gpg | 5.0 gpg |
Source: Penn State Agricultural Analytical Services Lab, Chester County summary (490 samples) and statewide summary (24,726 samples), tested 2007 to 2025. These are wells whose owners chose to test, often because of a problem, so rates may run higher than for all wells. Some tests had fewer samples than others.
Problems to watch for here
What to do next
- Test, if you haven't in a year. See testing options and prices.
- Read your results. Use our results tool, or upload a photo of your report.
- Get a fair quote if something needs fixing.
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