Pennsylvania Private Well Water Quality 2026

Pennsylvania’s PFAS Crisis in Private Wells

Pennsylvania private well water contamination is more widespread than most residents realise. According to a 2025 Penn State University study, 65% of the 167 wells sampled in 2023 and 2024 had detectable levels of PFAS, with 18% exceeding the EPA’s federal maximum contaminant levels. As Penn State civil engineering professor Heather Preisendanz noted, previous research has consistently found that more than half of private wells in Pennsylvania don’t meet drinking water standards overall — with around 40% of those failures due to health-related contaminants such as nitrate and bacteria.

Pennsylvania has the second highest number of residential wells of any state in the country, according to the US Geological Survey, with over 3.5 million residents depending on private well water. PFAS contamination is not evenly distributed. The Penn State researchers found the highest concentrations in the most developed parts of the state — particularly Montgomery County and southeastern Pennsylvania broadly. The counties of Blair, Bucks, Chester, Montgomery, and York showed the highest rates of PFAS exceedances across combined public and private water sources statewide.

The sources of PFAS in Pennsylvania groundwater are multiple and well-documented. Military bases in Bucks and Montgomery Counties used AFFF firefighting foam for decades. A 2025 national ATSDR study tested the blood of more than 1,300 Pennsylvania residents living near the former Naval Air Warfare Center Warminster and the Horsham Air Guard Station, and found that 99% had detectable PFAS in their blood — with private well owners in those communities having had exposure at levels thousands of times above the federal drinking water limit before contaminated wells were taken offline.

Beyond military bases, significant PFAS sources in Pennsylvania groundwater include:

• Industrial and manufacturing sites — Pennsylvania’s dense industrial history across the southeast has created a wide variety of PFAS point sources, including electronics manufacturing, metal plating, and chemical production facilities.
• Biosolids applied to farmland — research has found that agricultural land treated with PFAS-contaminated biosolids (treated wastewater sludge) poses a risk to nearby shallow wells, though the Penn State study found the relationship more complex than expected — developed land use was a stronger predictor than agricultural land in Pennsylvania specifically.
• Airports — commercial and regional airports that used AFFF foam are a documented PFAS source in groundwater across the state.
• Landfills — landfills accepting PFAS-containing consumer products can leach the chemicals into surrounding groundwater over time.

Pennsylvania set its own state MCLs for PFOS and PFOA in January 2023 — ahead of the federal rule — but these state limits are less stringent than the EPA’s 2024 federal limits of 4 ppt for both compounds. Critically, both state and federal PFAS standards apply only to public water systems. Private wells are entirely excluded from both.

Radon and Arsenic: Pennsylvania’s Hidden Geological Risks

Pennsylvania’s fractured bedrock geology creates a significant naturally occurring radon risk in groundwater. Radon-222 — a radioactive gas that dissolves readily in groundwater — is widespread across Pennsylvania’s bedrock aquifers. USGS baseline studies in multiple counties have found the majority of sampled private wells exceed the EPA’s proposed drinking water guideline of 300 picocuries per liter for radon. In Lycoming County, 50 of 75 sampled wells exceeded this level; in Clinton County, 59% of tested wells were above the proposed standard. Radon in drinking water adds to household radon exposure and is linked to an elevated risk of lung and stomach cancer with long-term exposure.

Arsenic is a further naturally occurring concern. USGS sampling in Lycoming County found 9 of 75 wells — 12% — contained arsenic above the federal limit of 10 ppb. Pennsylvania Department of Health analysis of USGS data across seven northern Pennsylvania counties confirmed arsenic as one of the metals most likely to exceed MCLs in private wells in that region. Arsenic is colourless and tasteless — it cannot be detected without laboratory testing — and long-term exposure is linked to cancers, cardiovascular disease, and nerve damage.

Nitrate, Bacteria, and Acid Mine Drainage

Coliform bacteria occur in approximately half of private wells and springs in Pennsylvania, according to Penn State Extension — one of the highest rates of any state. This is partly a function of the state’s unique well construction gap: with no statewide standards for how wells must be built, many older wells were never sealed or capped correctly, leaving direct pathways for surface contamination to enter the water supply. A Penn State Extension study sampling 701 private wells statewide found that approximately 40% failed at least one health-based drinking water standard, with bacteria as the most common finding.

Nitrate contamination from agricultural runoff is a documented risk in rural farming counties — particularly Lancaster and York, where intensive livestock and crop farming generates significant nutrient runoff into groundwater. Lancaster County alone has an estimated 38,000 private wells. High nitrate levels above 10 mg/L are particularly dangerous for infants under six months and can cause methemoglobinemia (blue baby syndrome). Critically, unlike bacteria, nitrates cannot be removed by boiling — they concentrate as the water evaporates.

Pennsylvania’s coal mining legacy creates a hazard unique to the state: acid mine drainage. Across the northeast and central regions — Lackawanna, Luzerne, Schuylkill, Carbon, and surrounding counties — mined coal seams expose pyrite to oxygen and water, generating sulfuric acid that drains into groundwater and streams. This contaminates nearby private wells with elevated iron, manganese, sulfates, and heavy metals. PA DEP’s Bureau of Mining Programs oversees abandoned mine remediation on an ongoing basis, but private wells near historic mining areas remain at risk and are not monitored.

Regulatory Situation for Pennsylvania Well Owners

Pennsylvania is in a category of its own when it comes to private well regulation. The PA Department of Environmental Protection explicitly states that it does not regulate private wells. Beyond that, Pennsylvania is believed to be the only state in the US with no statewide construction standards for private water wells — no rules governing how a well must be sited, cased, sealed, or capped. As Penn State Extension well water educator Jennifer Fetter stated: “I’m pretty positive, at this point, that we’re the only state without any well construction standards at all.” Even Alaska, which previously shared this status, has since introduced guidance for new well drilling.

There is no requirement for private well owners in Pennsylvania to test their water at any point — not when buying a property, not annually, not ever. There is no state notification system to alert well owners when contamination is detected in their area. According to Penn State Extension, an estimated 45% of private water sources in Pennsylvania are never tested. Complete responsibility for water safety sits with the homeowner.

Pennsylvania’s 2023 state PFAS MCLs (for PFOS and PFOA) and the EPA’s 2024 federal PFAS MCLs both apply only to public water systems. Private wells are excluded from both frameworks.

Check our Pennsylvania municipal water quality page for city-by-city tap water data, or use our live boil water notice tracker for active advisories across the state.

Known High-Risk Areas in Pennsylvania

If you live near any of the following locations, well water testing is urgent — not precautionary.

How to Test Your Pennsylvania Well Water — and What to Do Next

Given Pennsylvania’s contamination profile — widespread PFAS, elevated radon across much of the state, a high rate of bacterial contamination linked to the lack of construction standards, and localised acid mine drainage and nitrate risks — every private well owner in the state should test their water. Penn State Extension’s Master Well Owner Network recommends annual testing for coliform bacteria, nitrate, and pH as a minimum, with PFAS testing strongly recommended for all wells, and urgent testing for any well within the range of the high-risk areas listed above.

Penn State Extension runs a limited free testing programme for qualifying Pennsylvania well owners, funded through a CDC Environmental Health Capacity grant. Contact Penn State Extension at extension.psu.edu or your local county health department to locate a state-certified laboratory. PA DEP’s website at pa.gov/dep maintains a searchable list of accredited labs capable of testing for PFAS using EPA Methods 533 and 537.1.

For filter options, our well water filter guide covers reverse osmosis systems for PFAS, radon, and arsenic, UV disinfection for bacteria, and whole-house well systems for comprehensive treatment including acid mine drainage. You can also browse our full water filter solutions page or check your ZIP code for local water quality context.

For other states with similar PFAS and military-base contamination profiles, see our page on Michigan private well water. Return to the private well water directory to find your state.