Well water in Chester County, Pennsylvania

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Testing strongly recommended

tested well samples in Chester County exceeded the EPA limit for radium (226 + 228) (5 pCi/L), based on public data from USGS Water Quality Portal.

The strongest signal is total coliform: 29% of 460 local wells tested were above the EPA limit, too few samples to carry the headline but first on the test list below.

460 private wells tested 2008 to 2025 in state summaries; 12,005 test results across 13 contaminants from at least 896 wells, 1925 to 2026; nitrate has the most at 2,695. 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 211,418 people in Chester County get their drinking water from a private well, per USGS 2015 county water use. That is about 41% of residents.

Separately, the USGS national arsenic model estimates that <1% of the 211,418 people on private wells in Chester County draw water above 10 ug/L (the model's range is <1% to 1%), 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, 2008 to 2025. Shares are against the level the state applies to each contaminant, named in the last column; several are stricter than EPA.

Contaminant	Above state level	Wells tested	Median	Highest	State level
Total coliform	29%	460		228	0 MPN/100mL
Manganese	15%	229	10	10,400	50 ug/L
Iron	15%	233	100	28,500	300 ug/L
Lead (first draw)	9%	228		142	15 ug/L
Nitrate + nitrite as N	5%	211	3.5	15.5	10 mg/L
Chloride	4%	47	18.2	408	250 mg/L
E. coli	2%	460		36.4	0 MPN/100mL
Copper	2%	264	0.04	11.3	1.3 mg/L
Arsenic	1%	166		85	10 ug/L
Sodium		43	24.1	151

What individual samples found

Each row summarizes every public sample for that contaminant inside Chester County. 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
Radium (226 + 228) 1985 to 2018	22%	311	69%	0.78	184	5 pCi/L EPA limit
Nitrate 1925 to 2026	21%	2,695	92%	3.58	199	10 mg/L EPA limit
E. coli 1994 to 2021	9%	11	9%	0	3	0 MPN/100mL EPA limit
Lead 1973 to 2026	2%	705	50%	0	70	15 ug/L EPA limit
Arsenic 1974 to 2026	<1%	604	38%	0	69	10 ug/L EPA limit
Fluoride 1949 to 2026	<1%	1,000	40%	0	10	4 mg/L EPA limit
Copper 1973 to 2026	0%	598	64%	0.003	0.87	1.3 mg/L EPA limit
Uranium 1986 to 2025	0%	260	48%	0	11	30 ug/L EPA limit
Chloride 1925 to 2026	no limit	1,448	100%	12	2,100	250 mg/L nuisance level
Iron 1925 to 2026	no limit	1,280	70%	11.9	440,000	300 ug/L nuisance level
Manganese 1957 to 2026	no limit	1,255	77%	6	22,000	300 ug/L health guideline
Sodium 1925 to 2026	no limit	1,068	100%	7.6	160	20 mg/L health guideline
Radon 1986 to 2021	no limit	770	99%	1,700	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	21%2,095 samples	22%534 samples	50%34 samples	13%32 samples
Fluoride	<1%731 samples	0%239 samples	0%18 samples	0%12 samples
Lead	2%564 samples	<1%122 samples	n/a	0%12 samples
Arsenic	<1%428 samples	0%147 samples	n/a	0%22 samples
Copper	0%494 samples	0%85 samples	n/a	0%12 samples
Uranium	0%206 samples	0%43 samples	n/a	n/a

Nitrate above the limit in Chester County fell from 50% of 34 samples in the 2010s to 13% of 32 in the 2020s.

Fluoride, lead, arsenic, copper, uranium have held within a few points between the two most recent periods with enough samples.

Closer than the county

See the sampled wells near your address

The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.

Check my address

What this means

Among homeowners in Chester County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (29% of 460 wells), lead (9% of 228 wells), and nitrate (5% of 211 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 Chester County

1
Total coliform
29% of 460 local wells tested were above the EPA limit.
2
Radium (226 + 228)
22% of 311 local samples were above the limit.
3
Nitrate
21% of 2,695 local samples were above the limit.
4
Lead
9% of 228 local wells tested were above the EPA limit.
5
E. coli
9% of 11 local samples were above the limit.
6
Copper
2% of 264 local wells tested were above the EPA limit.
7
Arsenic
1% of 166 local wells tested were above the EPA limit.
8
Fluoride
<1% of 1,000 local samples were above the limit.

Test your Chester County well for total coliform, radium (226 + 228) and nitrate

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 $209 Already 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 Chester County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Chester County

13,743 domestic wells in Chester County are on record with the state. 100% are drilled into bedrock, and the typical well is 150 feet deep (one in ten goes past 360 feet).

In a typical Chester County well, bedrock starts about 36 feet down, the median yield is 12 gallons per minute, 8% 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 Chester County

Piedmont and Blue Ridge crystalline-rock aquifers

Igneous and metamorphic-rock. Granite and similar crystalline rock hold water only in fractures. Wells are deep and yields modest, and the rock itself is the source of arsenic, radon and uranium, which is why those three head the test list in bedrock country.

Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county 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

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Manganese

Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis

Iron

Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration

Radium (226 + 228)

Water softener (cation exchange); Point-of-use reverse osmosis

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 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 manganese

Iron and manganese oxidizing filter

whole-house, at the point of entry, about $1,800

Air-injection or greensand media; fixes staining at the source.

Free, no obligation

Get on the list for a free in-home water test in Chester County

No water treatment company serves Chester County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Chester County, and you get an email naming it first.

Common questions

How deep are wells in Chester County?

The typical domestic well in Chester County is 150 feet deep, based on 13,743 wells reported to the state. One in ten is deeper than 360 feet. 100% are drilled into bedrock.

Is there arsenic in well water in Chester County?

Arsenic was detected in 38% of 604 public well samples in Chester County, and <1% 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 Chester County?

The median radon level across 770 public samples in Chester County was 1,700 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 Chester County?

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.

Towns in Chester County

46 towns have fewer than 30 public samples and are included in the Chester County totals above rather than shown separately: Atglen borough, Avondale borough, Birmingham township, Caln township, Coatesville, Downingtown borough, East Caln township, East Coventry township, East Fallowfield township, East Goshen township, East Nantmeal township, Elk township, Elverson borough, Franklin township, Highland township, Honey Brook borough, Kennett Square borough, London Britain township, Londonderry township, Malvern borough, Modena borough, Newlin township, New London township, Oxford borough, Parkesburg borough, Pennsbury township, Penn township, Pocopson township, Sadsbury township, South Coatesville borough, South Coventry township, Spring City borough, Thornbury township, Upper Oxford township, Uwchlan township, Valley township, Wallace township, Warwick township, West Brandywine township, West Chester borough, West Grove borough, West Nantmeal township, West Pikeland township, West Sadsbury township, Westtown township, West Vincent township.

Counties near Chester County

Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.

Want the numbers themselves? Download the Pennsylvania dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 12,005 samples in Chester County. 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 Chester County, up to 460 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 211,418 people on private wells in Chester County 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: 23,160 well records in Chester County, 13,743 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.