Well water in Ohio

1in12

Testing recommended

tested well samples in Ohio exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal and Ohio EPA Washington County residential well PFAS sampling.

The strongest signal is PFOA: 56% of 742 local samples were above the limit, too few samples to carry the headline but first on the test list below.

58,883 test results across 17 contaminants from at least 2,036 wells, 1972 to 2026; chloride has the most at 16,515. Data refreshed September 22, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

Ohio EPA sampled residential wells around the Chemours Washington Works site in Washington County, and wells with a detection are resampled quarterly. PFAS shares describe wells near a known source, not every well in the county. In that targeted sampling, 56% of 742 PFOA results in Ohio were above the EPA limit of 4 ng/L. In that targeted sampling, 5% of 210 PFOS results in Ohio were above the EPA limit of 4 ng/L.

An estimated 1,861,023 people in Ohio get their drinking water from a private well, per USGS 2015 county water use.

Separately, the USGS national arsenic model estimates that 10% of the 1,861,023 people on private wells in Ohio draw water above 10 ug/L (the model's range is 6% to 16%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Ohio. 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
PFOA 2002 to 2025	56%	742	63%	20	22,100	4 ng/L EPA limit
Arsenic 1972 to 2023	8%	2,213	54%	0.26	382	10 ug/L EPA limit
PFOS 2019 to 2025	5%	210	13%	0	15	4 ng/L EPA limit
Lead 1972 to 2023	4%	2,669	32%	0	1,400	15 ug/L EPA limit
Nitrate 1972 to 2026	4%	5,282	61%	0.05	7,080	10 mg/L EPA limit
Fluoride 1972 to 2023	<1%	3,833	84%	0.27	7	4 mg/L EPA limit
Uranium 1982 to 2023	<1%	501	86%	0.604	430	30 ug/L EPA limit
E. coli 1999 to 2019	<1%	331	<1%	0	1	0 MPN/100mL EPA limit
Copper 1972 to 2023	<1%	2,477	45%	0	4.6	1.3 mg/L EPA limit
Radium (226 + 228) 1999 to 2020	0%	207	71%	0.13	1.8	5 pCi/L EPA limit
PFNA 2022 to 2025	0%	98	1%	0	2	10 ng/L EPA limit
PFHxS 2022 to 2025	0%	98	7%	0	7	10 ng/L EPA limit
Chloride 1972 to 2023	no limit	16,515	100%	41.1	320,000	250 mg/L nuisance level
Sodium 1972 to 2023	no limit	15,364	100%	22	100,000	20 mg/L health guideline
Iron 1972 to 2023	no limit	4,103	88%	700	957,000	300 ug/L nuisance level
Manganese 1972 to 2023	no limit	4,099	88%	70	82,000	300 ug/L health guideline
Radon 1991 to 2019	no limit	141	99%	340	1,930	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	2%4,123 samples	8%721 samples	7%244 samples	20%194 samples
Fluoride	1%2,491 samples	0%314 samples	0%979 samples	0%49 samples
Lead	7%1,406 samples	0%240 samples	1%974 samples	0%49 samples
Copper	<1%1,215 samples	0%240 samples	0%973 samples	0%49 samples
Arsenic	6%950 samples	13%244 samples	9%970 samples	4%49 samples
PFOA	n/a	54%199 samples	59%283 samples	56%260 samples

Nitrate above the limit in Ohio rose from 7% of 244 samples in the 2010s to 20% of 194 in the 2020s.

Arsenic above the limit in Ohio fell from 9% of 970 samples in the 2010s to 4% of 49 in the 2020s.

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

What this means

The contaminants most often above their limit here are pfoa (56% of 742 samples), arsenic (8% of 2,213 samples), and pfos (5% of 210 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.

What to test for in Ohio

1
PFOA
56% of 742 local samples were above the limit.
2
Arsenic
8% of 2,213 local samples were above the limit.
3
PFOS
5% of 210 local samples were above the limit.
4
Lead
4% of 2,669 local samples were above the limit.
5
Nitrate
4% of 5,282 local samples were above the limit.
6
Fluoride
<1% of 3,833 local samples were above the limit.
7
Uranium
<1% of 501 local samples were above the limit.
8
Volatile organic compounds (VOCs)
43,152 leaking underground storage tank sites on record locally.
9
Metals panel
1,995 hazardous waste sites on record locally.

Test your Ohio well for PFOA, arsenic and PFOS

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 Ohio: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Ohio numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Free, one email

Send me the Ohio report

The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.

Wells in Ohio

417,827 domestic wells in Ohio are on record with the state since 1970. 73% are drilled into bedrock, and the typical well is 96 feet deep (one in ten goes past 200 feet).

In a typical Ohio well, bedrock starts about 36 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.

52,721

1970s

35,982

1980s

71,558

1990s

75,888

2000s

38,722

2010s

9,559

2020s

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 ODNR water well log search and choose Water Well.
The log lists depth, depth to bedrock, casing, static water level, the pump test and the driller.

Ohio has required well logs since 1948, so most drilled wells have one.

The rock under Ohio

Mississippian 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 Ohio

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 Water Systems Program, Ohio Department of Health
Laboratory Certification, Ohio EPA

Contamination sources on record in Ohio

Ohio EPA records 43,152 leaking underground storage tank sites and 1,995 hazardous waste sites in Ohio, among 46,629 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.

43,152: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
1,995: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
587: lined landfills and transfer facilities
895: other remediation projects

Treatment that fits the local profile

PFOA

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

Arsenic

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

PFOS

Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange

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

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 PFOA

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For PFOA

Whole-house PFAS carbon system

whole-house, at the point of entry, about $3,000

Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.

For PFOA

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 PFOS

Aquasana Claryum 3-Stage under-sink filter

under-sink or countertop, about $175

Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.

For PFOS

Aquasana HealthShield whole-house filter

whole-house, at the point of entry, about $2,099

Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.

Common questions

How deep are wells in Ohio?

The typical domestic well in Ohio is 96 feet deep, based on 417,827 wells reported to the state since 1970. One in ten is deeper than 200 feet. 73% are drilled into bedrock.

Is there arsenic in well water in Ohio?

Arsenic was detected in 54% of 2,213 public well samples in Ohio, 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 Ohio?

The median radon level across 141 public samples in Ohio was 340 pCi/L, with a high of 1,930 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Ohio?

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 Ohio

2 counties have fewer than 30 public samples and are included in the Ohio totals above rather than shown separately: Cuyahoga, Erie.

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

Sources

USGS Water Quality Portal: 57,959 samples in Ohio. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
Ohio EPA Washington County residential well PFAS sampling: 924 samples in Ohio. Residential well PFAS results from Ohio EPA's Washington County drinking water investigation (sampling by AECOM), published on the Ohio EPA GIS server. Retrieved September 22, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 1,861,023 people on private wells in Ohio 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.
Ohio DNR water well logs: 549,315 well records in Ohio, 417,827 domestic. Water well logs filed with the Ohio Department of Natural Resources Division of Water Resources since 1948. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 17, 2026.
Ohio EPA regulated sites: 46,629 regulated sites located in Ohio. Remediation sites, leaking underground storage tank releases (BUSTR) and landfills from the Ohio Environmental Protection Agency and the Division of State Fire Marshal. Retrieved September 17, 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.