Well Water Notebook
Information only, not medical advice. We never say whether your water is safe to drink. Ask a state-certified lab or your local health department. Disclaimer

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Well water testing in Chester County, Pennsylvania

In the Penn State lab data for Chester County, bacteria, out-of-range pH, iron and manganese show up most often. Here's what the data show, what Pennsylvania recommends, and where to get a sample analyzed, with a source for every fact.

This page can't tell you whether your water is safe to drink. Only a test of your well can do that. For help, contact a DEP-accredited lab or the DEP office below.

How many people here use a private well

USGS estimates that about 211,000 people in Chester County supplied their own household water in 2015, about 41% of the county's population.1 Statewide, Penn State Extension says over one million rural homes and farms use a private well or spring.2

Does Pennsylvania require testing?

No. Penn State Extension says there are no statewide regulations requiring testing of private wells and springs. Testing is the homeowner's voluntary responsibility.2

What tests in Chester County have found

The Penn State Agricultural Analytical Services Laboratory (AASL) publishes a summary of drinking water samples it has tested from each county. For Chester County, the summary covers 490 samples from 1/18/2008 - 6/9/2025:3

Test Counted as failing Samples failing Percent
Total coliform bacteria present (standard: 0) 135 of 460 29.3%
E. coli bacteria present (standard: 0) 10 of 460 2.2%
Nitrate + nitrite (as N) over 10 mg/L 11 of 211 5.2%
pH (secondary standard) outside 6.5–8.5 112 of 383 29.2%
Iron (secondary standard) over 0.3 mg/L 34 of 233 14.6%
Manganese (secondary standard) over 0.05 mg/L 34 of 229 14.8%
Lead, first draw over 0.015 mg/L 21 of 228 9.2%
Arsenic over 0.01 mg/L 2 of 166 1.2%

These are samples homeowners chose to send to one lab, not a random survey. Penn State presents the summaries as a guide to which problems are most common locally, to help you decide what to test.2 Iron, manganese and pH have secondary (aesthetic) standards, not health-based limits.4

A USGS national model estimates that about 1,700 domestic-well users in Chester County (95% confidence range about 1,100–2,500, based on 2010 population) have well water with predicted arsenic above 10 µg/L.5 That's a model estimate and can't predict any single well.

What to test and how often

PA DEP recommends testing your well every year for total coliform bacteria, nitrates, total dissolved solids and pH, plus anything else you suspect, using a state-certified lab.6 Penn State's county summaries are meant to help you decide what else to add.2

Where to get tested and treatment options

Bacteria test kits: DEP says bacterial test kits can be bought from its regional offices. For Chester County, that's DEP's Southeast Regional Office (serving Bucks, Chester, Delaware, Montgomery and Philadelphia): John Cairnes, 484-250-5106.6

Accredited labs: DEP publishes lists of labs certified for chemical testing and bacteriological testing (PDFs dated June 2024).6 The Penn State AASL also offers drinking water test packages for well and spring owners.2

The Chester County Health Department lists these well water testing labs in Chester County (it also lists labs in nearby counties):7

Lab Address Phone
Brandywine Science Center, Inc. 204 Line Road, Kennett Square 610-444-9850
H.O. Thompson Testing Lab 104 Valley View Drive, Parkesburg 610-593-5030

Confirm with any lab that it's accredited for each test you need.

If a result is high: DEP says that if results are higher than Pennsylvania's MCLs, you should install a treatment device for that specific contaminant, and it points to NSF's treatment resources and certified product database.6 Our guides cover what agencies say works:

  1. Dieter, C.A., and others, 2018, Estimated Use of Water in the United States County-Level Data for 2015 (ver. 2.0), U.S. Geological Survey data release (domestic self-supplied population). https://doi.org/10.5066/F7TB15V5 ↩

  2. Penn State Extension, "County Summaries of Pennsylvania Groundwater Well and Spring Data" (updated September 28, 2026). https://extension.psu.edu/county-summaries-of-pennsylvania-groundwater-well-and-spring-data ↩↩↩↩↩

  3. Penn State Agricultural Analytical Services Laboratory, "Summary of Drinking Water Samples Tested: Chester County." https://agsci.psu.edu/aasl/water-testing/drinking-water-testing/drinking-water-test-summaries/chester ↩

  4. U.S. EPA, "Secondary Drinking Water Standards: Guidance for Nuisance Chemicals." https://www.epa.gov/sdwa/secondary-drinking-water-standards-guidance-nuisance-chemicals ↩

  5. Ayotte, J.D., Medalie, L., and Qi, S.L., 2017, Estimated county level domestic well population with arsenic greater than 10 micrograms per liter based on probability estimates for the conterminous U.S., U.S. Geological Survey data release. https://doi.org/10.5066/F7CN724V ↩

  6. Pennsylvania DEP, "Private Wells: Water Testing." https://www.pa.gov/agencies/dep/residents/my-water/private-wells/water-testing ↩↩↩↩

  7. Chester County Health Department, "Well Water Testing Labs in Chester County." https://www.chesco.org/978/Well-Water-Test-Labs ↩