State Well Water Guide
Pennsylvania Private Well Water Guide
Approximately 26% of Pennsylvania residents — about 3.3 million people — rely on private wells, making Pennsylvania one of the largest private well populations on the East Coast. Pennsylvania's geology creates diverse contamination risks: naturally occurring radon and radium in granite areas, arsenic in the southeast and northwest, iron and manganese statewide, and significant PFAS contamination near military installations and industrial sites. The Marcellus Shale natural gas drilling boom has also raised methane migration and spill contamination concerns for rural wells. Pennsylvania does not require private well testing, leaving the burden on individual homeowners.
Testing Guidance
Penn State Extension recommends testing private wells annually for bacteria and nitrates, and every 3–5 years for a comprehensive panel. Radon testing is recommended for all well owners — Pennsylvania has the highest radon levels in the nation due to its uranium-rich bedrock. Arsenic testing is important in Chester, Lancaster, York, Delaware, and Erie counties. PFAS testing is warranted near Willow Grove NAS, Horsham Township (one of the most contaminated PFAS sites in the country), Fort Indiantown Gap, and Letterkenny Army Depot.
What to Test For in Pennsylvania
Total coliform bacteria and E. coli — annual minimum for all wells
Nitrates — annual for agricultural areas and wells near septic systems
Radon — all Pennsylvania wells; the state has the highest radon concentrations in the U.S.
Arsenic — particularly southeastern PA (Chester, Lancaster, Delaware counties) and northwestern PA
Radium — granite and gneiss bedrock regions of southeastern Pennsylvania
Iron and manganese — widespread statewide
PFAS — Horsham, Montgomery County, and areas near military installations across the state
Methane — wells within 1 mile of active or abandoned Marcellus Shale gas wells
pH — low-pH water accelerates lead leaching from plumbing
Common Contamination Risks in Pennsylvania
Radon — Pennsylvania's granite and uranium-rich bedrock makes it the highest-radon state in the nation; radon in well water off-gasses into indoor air
PFAS contamination — Horsham Township in Montgomery County is one of the most severely PFAS-contaminated communities in the U.S., with groundwater contamination from Willow Grove NAS exceeding 1,000 ppt PFOA/PFOS
Arsenic from natural geological sources in the Piedmont and Reading Prong geological formations
Iron and manganese causing aesthetic problems in wells across the state
Methane migration from natural gas drilling activity in northern and southwestern Pennsylvania
Agricultural nitrate contamination in Lancaster, Lebanon, and York counties — Pennsylvania's most intensively farmed counties
Contaminant Guides Relevant to PA Wells
PFAS
Synthetic Chemicals
EPA limit: 4 ppt
Lead
Heavy Metals
EPA limit: 15 ppb (action level)
Nitrates
Agricultural Chemicals
EPA limit: 10 mg/L
DBPs
Disinfection Byproducts
EPA limit: 80 µg/L (TTHMs) / 60 µg/L (HAA5)
Arsenic
Heavy Metals
EPA limit: 10 ppb
Hard Water
Minerals
EPA limit: No federal limit
Chlorine
Disinfection Chemicals
EPA limit: 4 mg/L (MRDL)
Microplastics
Emerging Contaminants
EPA limit: No federal limit
Bacteria
Microbial Contamination
EPA limit: Zero E. coli / < 1 coliform per 100 mL
Fluoride
Minerals
EPA limit: 4 mg/L (MCL) / 2 mg/L (Secondary MCL)
Chromium-6
Heavy Metals
EPA limit: 100 ppb (total chromium)
Copper
Heavy Metals
EPA limit: 1.3 mg/L (action level)
Radon
Radioactive Contaminants
EPA limit: No finalized MCL
Iron & Manganese
Minerals
EPA limit: 0.3 mg/L iron / 0.05 mg/L manganese (aesthetic SMCLs)
Atrazine
Agricultural Chemicals
EPA limit: 3 ppb (0.003 mg/L)
Uranium
Radioactive Contaminants
EPA limit: 30 µg/L (30 ppb)
Perchlorate
Industrial Chemicals
EPA limit: 0.056 mg/L (56 ppb)
VOCs
Industrial Chemicals
EPA limit: Varies by compound: benzene 5 ppb; TCE 5 ppb; PCE 5 ppb; vinyl chloride 2 ppb
Radium
Radioactive Contaminants
EPA limit: 5 pCi/L (combined Ra-226 + Ra-228)
Crypto & Giardia
Microbial Contamination
EPA limit: Zero (treatment technique standard)
Hydrogen Sulfide
Naturally Occurring Compounds
EPA limit: No MCL; Secondary MCL (aesthetic) of 0.05 mg/L
Selenium
Minerals
EPA limit: 50 ppb (0.05 mg/L)
Cadmium
Heavy Metals
EPA limit: 5 ppb (0.005 mg/L)
Mercury
Heavy Metals
EPA limit: 2 ppb (0.002 mg/L)
Barium
Heavy Metals
EPA limit: 2 mg/L
pH
Water Quality Indicators
EPA limit: 6.5–8.5 (secondary standard)
Find a Certified Lab in Pennsylvania
Use the Pennsylvania state-certified laboratory program to find accredited labs for private well testing. Always verify current certification before submitting samples.
PA Certified Lab Directory ↗Pennsylvania Well Water FAQs
Related Pages
Data Sources & Provenance
All data on this page is sourced from official U.S. government or public datasets.
Quick Reference
State program
PA Certified Labs ↗EPA guidance
EPA Private Wells Program ↗State lab directory
PA Certified Labs ↗Minimum Annual Tests
Plus state-specific contaminants listed above
Other State Guides