Well water in Mercer County, PA
What Penn State well tests show for Mercer County, compared with Pennsylvania as a whole.
In short
About 43% of the Mercer County well samples Penn State tested were positive for coliform bacteria, close to the statewide rate. Compared with the rest of Pennsylvania, it stands out for iron (28% vs. 17% statewide).
What local well tests found
43%failed for coliform bacteria
62%were corrosive to plumbing
27%had manganese over the stain level
| Test (share of samples over the guideline) | Mercer County | Pennsylvania |
|---|---|---|
| Total coliform bacteria | 43.4% | 44.1% |
| E. coli bacteria | 6.8% | 10.6% |
| Corrosivity (likely to eat pipes) | 61.5% | 65.9% |
| pH outside 6.5 to 8.5 | 10.6% | 16.6% |
| Manganese (stains) | 27.4% | 22.3% |
| Iron (stains) | 27.8% | 17.2% |
| Lead, first-draw sample | 6.5% | 8.9% |
| Arsenic | 6.1% | 5.5% |
| Nitrate | 5.3% | 4.1% |
| Typical hardness (median) | 4.6 gpg | 5.0 gpg |
Source: Penn State Agricultural Analytical Services Lab, Mercer County summary (299 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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