Well water in Dauphin County, Pennsylvania

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Testing strongly recommended

private wells tested between 2007 and 2025 in Dauphin County had total coliform above the EPA limit (0 MPN/100mL), according to the Penn State water testing lab.

321 private wells tested 2007 to 2025 in state summaries; 1,295 test results across 12 contaminants from at least 128 wells, 1931 to 2026; iron has the most at 225. 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 74,878 people in Dauphin County get their drinking water from a private well, per USGS 2015 county water use. That is about 27% of residents.

Separately, the USGS national arsenic model estimates that 3% of the 74,878 people on private wells in Dauphin County draw water above 10 ug/L (the model's range is 2% to 5%), 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.

Contaminant	Above state level	Wells tested	Median	Highest	State level
Total coliform	40%	321		378	0 MPN/100mL
Manganese	20%	153	10	2,610	50 ug/L
Iron	16%	150	100	11,400	300 ug/L
Lead (first draw)	10%	138		57	15 ug/L
Arsenic	7%	90		27	10 ug/L
E. coli	7%	321		201	0 MPN/100mL
Nitrate + nitrite as N	3%	144	2.9	11.3	10 mg/L
Copper	1%	165	0.02	3.41	1.3 mg/L
Chloride	0%	21	11.8	211	250 mg/L
Sodium		42	15.0	230

What individual samples found

Each row summarizes every public sample for that contaminant inside Dauphin 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
Nitrate 1931 to 2026	17%	187	98%	2.9	57.5	10 mg/L EPA limit
Arsenic 1972 to 2023	8%	78	88%	1.05	48	10 ug/L EPA limit
Fluoride 1953 to 2023	0%	125	83%	0.1	0.6	4 mg/L EPA limit
Lead 1972 to 2023	0%	51	100%	0	0.749	15 ug/L EPA limit
Uranium 1993 to 2023	0%	16	44%	0	16	30 ug/L EPA limit
Iron 1931 to 2023	no limit	225	83%	240	16,300	300 ug/L nuisance level
Manganese 1956 to 2023	no limit	213	85%	90	5,650	300 ug/L health guideline
Sodium 1953 to 2023	no limit	184	97%	5.25	67.1	20 mg/L health guideline
Chloride 1931 to 2023	no limit	152	85%	4	83	250 mg/L nuisance level
Radon 1993 to 2023	no limit	48	100%	1,800	4,600	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: Copper (9), E. coli (7).

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	22%139 samples	0%34 samples	n/a	0%10 samples
Arsenic	9%46 samples	8%26 samples	n/a	n/a

Nitrate above the limit in Dauphin County fell from 22% of 139 samples before 2000 to 0% of 34 in the 2000s.

Arsenic has 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 Dauphin County who sent a sample to the state lab, the health-based limits most often exceeded were total coliform (40% of 321 wells), lead (10% of 138 wells), and arsenic (7% of 90 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 Dauphin County

1
Total coliform
40% of 321 local wells tested were above the EPA limit.
2
Nitrate
17% of 187 local samples were above the limit.
3
Lead
10% of 138 local wells tested were above the EPA limit.
4
Arsenic
8% of 78 local samples were above the limit.
5
E. coli
7% of 321 local wells tested were above the EPA limit.
6
Copper
1% of 165 local wells tested were above the EPA limit.
7
Radon
Median local reading is 1,800 pCi/L.
8
Manganese
20% of 153 local wells tested were above the EPA secondary standard.

Test your Dauphin County well for total coliform, nitrate and lead

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

Wells in Dauphin County

7,011 domestic wells in Dauphin County are on record with the state. 99% are drilled into bedrock, and the typical well is 200 feet deep (one in ten goes past 340 feet).

In a typical Dauphin County well, bedrock starts about 31 feet down, the median yield is 15 gallons per minute, 5% 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 Dauphin County

Valley and Ridge 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 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

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

E. coli

Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system

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 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.

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.

Free, no obligation

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

No water treatment company serves Dauphin 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 Dauphin County, and you get an email naming it first.

Common questions

How deep are wells in Dauphin County?

The typical domestic well in Dauphin County is 200 feet deep, based on 7,011 wells reported to the state. One in ten is deeper than 340 feet. 99% are drilled into bedrock.

Is there arsenic in well water in Dauphin County?

Arsenic was detected in 88% of 78 public well samples in Dauphin County, and 8% 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 Dauphin County?

The median radon level across 48 public samples in Dauphin County was 1,800 pCi/L, with a high of 4,600 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Dauphin 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 Dauphin County

Wiconisco township67 samples

39 towns have fewer than 30 public samples and are included in the Dauphin County totals above rather than shown separately: Berrysburg borough, Conewago township, Dauphin borough, Derry township, East Hanover township, Elizabethville borough, Gratz borough, Halifax borough, Halifax township, Harrisburg, Highspire borough, Hummelstown borough, Jackson township, Jefferson township, Londonderry township, Lower Paxton township, Lower Swatara township, Lykens borough, Lykens township, Middle Paxton township, Middletown borough, Mifflin township, Millersburg borough, Paxtang borough, Penbrook borough, Pillow borough, Reed township, Royalton borough, Rush township, South Hanover township, Steelton borough, Susquehanna township, Swatara township, Upper Paxton township, Washington township, Wayne township, West Hanover township, Williamstown borough, Williams township.

Counties near Dauphin 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: 1,295 samples in Dauphin 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 Dauphin County, up to 321 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 74,878 people on private wells in Dauphin 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: 11,282 well records in Dauphin County, 7,011 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.