Well water in Pennsylvania
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Testing strongly recommended
private wells tested between 2007 and 2025 in Pennsylvania had total coliform above the EPA limit (0 MPN/100mL), according to the Penn State water testing lab.
22,730 private wells tested 2007 to 2025 in state summaries; 93,336 test results across 15 contaminants from at least 6,426 wells, 1901 to 2026; nitrate has the most at 19,172. Data refreshed September 16, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
These are samples homeowners paid to send to the Penn State lab, often because of a suspected problem, so shares above the limit run higher than a random survey would find.
An estimated 3,470,761 people in Pennsylvania get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that 2% of the 3,470,761 people on private wells in Pennsylvania draw water above 10 ug/L (the model's range is 2% to 4%), from geology and well depth rather than local tests.
What homeowner tests found
Penn State Agricultural Analytical Services Lab drinking water summaries: private wells tested and reported to the state, 2007 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA. County and state figures combine the town summaries, weighted by wells tested; medians are not combined.
| Contaminant | Above state level | Wells tested | Median | 95th pct | Highest | State level |
|---|---|---|---|---|---|---|
| Total coliform | 22,730 | 2420 | 0 MPN/100mL | |||
| Manganese | 7,691 | 60,680 | 50 ug/L | |||
| Iron | 7,683 | 225,300 | 300 ug/L | |||
| E. coli | 22,730 | 1046 | 0 MPN/100mL | |||
| Lead (first draw) | 6,163 | 2,039 | 15 ug/L | |||
| Arsenic | 5,555 | 354 | 10 ug/L | |||
| Nitrate + nitrite as N | 8,840 | 218 | 10 mg/L | |||
| Chloride | 3,000 | 3966 | 250 mg/L | |||
| Copper | 8,923 | 68.7 | 1.3 mg/L | |||
| Sodium | 1,088 | 2040 |
What individual samples found
Each row summarizes every public sample for that contaminant inside Pennsylvania. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Nitrate 1901 to 2026 | 19,172 | 85% | 2.2 | 690 | 10 mg/L EPA limit | |
| PFOA 2018 to 2025 | 86 | 31% | 0 | 29 | 4 ng/L EPA limit | |
| Radium (226 + 228) 1985 to 2022 | 814 | 75% | 0.24 | 184 | 5 pCi/L EPA limit | |
| PFOS 2018 to 2025 | 86 | 27% | 0 | 13 | 4 ng/L EPA limit | |
| E. coli 1994 to 2025 | 1,052 | 12% | 0 | 300 | 0 MPN/100mL EPA limit | |
| Arsenic 1901 to 2026 | 6,088 | 46% | 0 | 20,000 | 10 ug/L EPA limit | |
| Lead 1901 to 2026 | 6,183 | 52% | 0 | 2,000 | 15 ug/L EPA limit | |
| Copper 1901 to 2026 | 5,269 | 66% | 0.003 | 7 | 1.3 mg/L EPA limit | |
| Fluoride 1901 to 2026 | 7,998 | 73% | 0.1 | 29 | 4 mg/L EPA limit | |
| Uranium 1985 to 2026 | 2,293 | 66% | 0.13 | 64.8 | 30 ug/L EPA limit | |
| Chloride 1901 to 2026 | no limit | 11,419 | 98% | 9.6 | 78,900 | 250 mg/L nuisance level |
| Iron 1901 to 2026 | no limit | 11,337 | 85% | 190 | 3,200,000 | 300 ug/L nuisance level |
| Manganese 1901 to 2026 | no limit | 9,831 | 86% | 40 | 800,000 | 300 ug/L health guideline |
| Sodium 1901 to 2026 | no limit | 9,118 | 99% | 7.73 | 22,000 | 20 mg/L health guideline |
| Radon 1986 to 2025 | no limit | 2,590 | 99% | 1,100 | 53,000 | 2,000 pCi/L health guideline |
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Nitrate | 29%13,670 samples | 32%1,775 samples | 14%2,736 samples | 6%991 samples |
| Fluoride | <1%5,391 samples | <1%431 samples | 0%1,460 samples | <1%716 samples |
| Lead | 3%3,911 samples | <1%279 samples | 0%1,270 samples | 0%723 samples |
| Arsenic | 11%3,362 samples | 6%592 samples | 2%1,381 samples | 1%753 samples |
| Copper | <1%3,006 samples | 0%242 samples | 0%1,278 samples | 0%743 samples |
| Uranium | <1%617 samples | 0%186 samples | 0%1,185 samples | <1%305 samples |
Nitrate above the limit in Pennsylvania fell from 14% of 2736 samples in the 2010s to 6% of 991 in the 2020s.
Fluoride, lead, arsenic, copper, uranium have held within a few points between the two most recent periods with enough samples.
What this means
Among homeowners in Pennsylvania who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (44% of 22,730 wells), E. coli (11% of 22,730 wells), and lead (9% of 6,163 wells). These are ordinary wells tested by their owners, so the shares are the best available picture of a typical well here, with one caveat: people test more often when they suspect a problem.
Manganese and iron exceed the state's advisory level in a sizable share of wells; these are mostly a taste, staining or diet issue rather than a toxicity one.
What to test for in Pennsylvania
- 1Total coliform44% of 22,730 local wells tested were above the EPA limit.
- 2Nitrate26% of 19,172 local samples were above the limit.
- 3PFOA14% of 86 local samples were above the limit.
- 4Radium (226 + 228)13% of 814 local samples were above the limit.
- 5PFOS13% of 86 local samples were above the limit.
- 6E. coli11% of 22,730 local wells tested were above the EPA limit.
- 7Lead9% of 6,163 local wells tested were above the EPA limit.
- 8Arsenic7% of 6,088 local samples were above the limit.
Test your Pennsylvania well for total coliform, nitrate and PFOA
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in Pennsylvania: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Pennsylvania numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in Pennsylvania
263,159 domestic wells in Pennsylvania are on record with the state. 98% are drilled into bedrock, and the typical well is 175 feet deep (one in ten goes past 393 feet).
In a typical Pennsylvania well, bedrock starts about 28 feet down, the median yield is 12 gallons per minute, 9% of wells yield under 3 gallons per minute and usually need a storage tank.
Bedrock wells are where arsenic, uranium and radon come from: the water sits in fractures in granite and metamorphic rock and picks up whatever the rock carries. That is why testing for those three matters more here than in a dug or gravel well.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open PaGWIS (Pennsylvania Geological Survey) and choose Water Well.
- The record lists depth, depth to bedrock, yield and use; drillers have reported new wells to the state since 1966.
Pennsylvania has no private well construction standard and does not require testing, so many older wells have no record at all.
The rock under Pennsylvania
Valley and Ridge carbonate-rock aquifers
Sandstone and carbonate-rock. Layered sandstone and limestone means a well may draw from either. Hardness and iron are routine, and the limestone layers can carry bacteria and nitrate from the surface quickly, so test for both yearly.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the state centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Pennsylvania
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- Private Wells, PA DEP
- Laboratory Accreditation Program, PA DEP
Treatment that fits the local profile
Total coliform
Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
E. coli
Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
Lead
Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Manganese
Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For total coliform
Aquasana Rhino Well Water with UV
whole-house, at the point of entry, about $2,871
Whole-house system built for wells: sediment pre-filter, KDF and carbon, and a UV lamp rated to kill 99.99% of bacteria and viruses. It does not remove arsenic, nitrate, uranium or radon.
For E. coli
UV disinfection system
whole-house, at the point of entry, about $900
Fix the well cap and casing first; UV keeps bacteria from returning.
For lead
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For lead
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
For lead
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For arsenic
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
Common questions
How deep are wells in Pennsylvania?
The typical domestic well in Pennsylvania is 175 feet deep, based on 263,159 wells reported to the state. One in ten is deeper than 393 feet. 98% are drilled into bedrock.
Is there arsenic in well water in Pennsylvania?
Arsenic was detected in 46% of 6,088 public well samples in Pennsylvania, and 7% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Pennsylvania?
The median radon level across 2,590 public samples in Pennsylvania was 1,100 pCi/L, with a high of 53,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Pennsylvania?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Counties in Pennsylvania
- Adams49% total coliform
- Allegheny55% total coliform
- Armstrong70% total coliform
- Beaver52% total coliform
- Bedford47% total coliform
- Berks40% total coliform
- Blair34% total coliform
- Bradford48% total coliform
- Bucks32% total coliform
- Butler45% total coliform
- Cambria55% total coliform
- Cameron69% total coliform
- Carbon29% total coliform
- Centre43% total coliform
- Chester29% total coliform
- Clarion53% total coliform
- Clearfield71% total coliform
- Clinton51% total coliform
- Columbia45% total coliform
- Crawford44% total coliform
- Cumberland42% total coliform
- Dauphin40% total coliform
- Delaware32% total coliform
- Elk59% total coliform
- Erie52% total coliform
- Fayette60% total coliform
- Forest62% total coliform
- Franklin40% total coliform
- Fulton53% total coliform
- Greene75% total coliform
- Huntingdon45% total coliform
- Indiana56% total coliform
- Jefferson63% total coliform
- Juniata47% total coliform
- Lackawanna33% total coliform
- Lancaster42% total coliform
- Lawrence33% total coliform
- Lebanon36% total coliform
- Lehigh34% total coliform
- Luzerne38% total coliform
- Lycoming44% total coliform
- McKean58% total coliform
- Mercer43% total coliform
- Mifflin43% total coliform
- Monroe33% total coliform
- Montgomery36% total coliform
- Montour44% total coliform
- Northampton46% total coliform
- Northumberland46% total coliform
- Perry44% total coliform
- Philadelphia37% total coliform
- Pike25% total coliform
- Potter49% total coliform
- Schuylkill52% total coliform
- Snyder51% total coliform
- Somerset47% total coliform
- Sullivan38% total coliform
- Susquehanna40% total coliform
- Tioga49% total coliform
- Union39% total coliform
- Venango53% total coliform
- Warren42% total coliform
- Washington68% total coliform
- Wayne28% total coliform
- Westmoreland54% total coliform
- Wyoming41% total coliform
- York46% total coliform
Want the numbers themselves? Download the Pennsylvania dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 93,336 samples in Pennsylvania. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
- Penn State Agricultural Analytical Services Lab drinking water summaries: summaries for 10 contaminants in Pennsylvania, up to 22,730 wells each. County summaries of private water samples tested by the Penn State Agricultural Analytical Services Laboratory since 2007, published by the College of Agricultural Sciences. Counts are samples, not distinct wells. Shares are against the standard the lab prints: the EPA maximum contaminant level, or the secondary standard for iron, manganese and chloride. Lead is the first-draw result. Medians printed as 0.00 are stored as null because the lab rounds to two decimals. Retrieved September 16, 2026.
- USGS national arsenic model (Ayotte 2017): estimated share of 3,470,761 people on private wells in Pennsylvania above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- Pennsylvania Groundwater Information System (PaGWIS) wells: 408,022 well records in Pennsylvania, 263,159 domestic. Water well records from the Pennsylvania Groundwater Information System, Pennsylvania Geological Survey (DCNR). Only aggregates are shown; owner names and addresses are never stored. Retrieved September 16, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.