Well water in Oklahoma

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Testing strongly recommended

tested well samples in Oklahoma exceeded the EPA limit for nitrate (10 mg/L), based on public data from USGS Water Quality Portal.

39,970 test results across 14 contaminants from at least 4,350 wells, 1923 to 2022; nitrate has the most at 10,968. Data refreshed September 15, 2026.

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

An estimated 356,860 people in Oklahoma get their drinking water from a private well, per USGS 2015 county water use.

Separately, the USGS national arsenic model estimates that 1% of the 356,860 people on private wells in Oklahoma draw water above 10 ug/L (the model's range is <1% to 2%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Oklahoma. 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 1923 to 2022	35%	10,968	93%	6.15	352	10 mg/L EPA limit
Arsenic 1975 to 2021	16%	2,892	47%	0	300	10 ug/L EPA limit
Uranium 1977 to 2021	8%	1,135	81%	1.55	1,500	30 ug/L EPA limit
Lead 1951 to 2021	3%	1,636	26%	0	1,600	15 ug/L EPA limit
Fluoride 1938 to 2021	3%	2,932	96%	0.3	70	4 mg/L EPA limit
Copper 1970 to 2021	<1%	2,321	36%	0	520	1.3 mg/L EPA limit
Radium (226 + 228) 1982 to 2021	0%	226	83%	0.2	3.4	5 pCi/L EPA limit
Chloride 1923 to 2022	no limit	5,707	94%	28	194,000	250 mg/L nuisance level
Iron 1923 to 2021	no limit	4,287	71%	30	2,090,000	300 ug/L nuisance level
Sodium 1942 to 2021	no limit	3,763	99%	47	82,900	20 mg/L health guideline
Manganese 1949 to 2021	no limit	3,750	60%	0.28	680,000	300 ug/L health guideline
Radon 1982 to 2018	no limit	347	94%	230	6,200	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: PFOS (3), PFOA (3).

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	17%3,424 samples	38%5,576 samples	58%1,943 samples	0%25 samples
Fluoride	3%2,342 samples	<1%490 samples	0%97 samples	n/a
Arsenic	12%2,160 samples	31%595 samples	22%134 samples	n/a
Copper	<1%1,744 samples	0%463 samples	3%111 samples	n/a
Lead	4%1,278 samples	0%244 samples	0%111 samples	n/a
Uranium	8%765 samples	9%256 samples	7%111 samples	n/a

Nitrate above the limit in Oklahoma fell from 58% of 1943 samples in the 2010s to 0% of 25 in the 2020s.

Arsenic above the limit in Oklahoma fell from 31% of 595 samples in the 2000s to 22% of 134 in the 2010s.

Fluoride, copper, lead, uranium 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 nitrate (35% of 10,968 samples), arsenic (16% of 2,892 samples), and uranium (8% of 1,135 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 Oklahoma

1
Nitrate
35% of 10,968 local samples were above the limit.
2
Arsenic
16% of 2,892 local samples were above the limit.
3
Uranium
8% of 1,135 local samples were above the limit.
4
Lead
3% of 1,636 local samples were above the limit.
5
Fluoride
3% of 2,932 local samples were above the limit.
6
Copper
<1% of 2,321 local samples were above the limit.
7
Coliform bacteria
Recommended for every private well, every year.
8
Volatile organic compounds (VOCs)
18 hazardous waste sites on record locally.
9
Metals panel
18 hazardous waste sites on record locally.

Test your Oklahoma well for nitrate, arsenic and uranium

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 Oklahoma: certified labs, state programs and prices.

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

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Send me the Oklahoma report

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

Wells in Oklahoma

93,526 domestic wells in Oklahoma are on record with the state since 1970. the typical well is 160 feet deep (one in ten goes past 300 feet).

In a typical Oklahoma well, the median yield is 18 gallons per minute, 6% of wells yield under 3 gallons per minute and usually need a storage tank.

435

1970s

13,894

1980s

16,170

1990s

25,149

2000s

18,786

2010s

16,824

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 OWRB well log search and choose Water Well.
It lists depth, first water, yield and the driller.

Oklahoma has required well logs since 1972.

The rock under Oklahoma

Not a principal aquifer

The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.

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 Oklahoma

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.

Technical Assistance (private citizen well water testing), Oklahoma DEQ
Laboratory Accreditation, Oklahoma DEQ

Contamination sources on record in Oklahoma

Oklahoma DEQ land sites records 18 hazardous waste sites in Oklahoma, among 238 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.

18: hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
46: lined landfills and transfer facilities
77: other remediation projects
97: other solid waste facilities

Treatment that fits the local profile

Nitrate

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

Arsenic

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

Uranium

Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange

Lead

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

Fluoride

Point-of-use reverse osmosis; Activated alumina; 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 nitrate

Under-sink reverse osmosis system

under-sink or countertop, about $300

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

For nitrate

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 lead

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 lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

Common questions

How deep are wells in Oklahoma?

The typical domestic well in Oklahoma is 160 feet deep, based on 93,526 wells reported to the state since 1970. One in ten is deeper than 300 feet.

Is there arsenic in well water in Oklahoma?

Arsenic was detected in 47% of 2,892 public well samples in Oklahoma, and 16% 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 Oklahoma?

The median radon level across 347 public samples in Oklahoma was 230 pCi/L, with a high of 6,200 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Oklahoma?

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 Oklahoma

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

Sources

USGS Water Quality Portal: 39,970 samples in Oklahoma. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 356,860 people on private wells in Oklahoma 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.
Oklahoma OWRB reported well logs: 136,746 well records in Oklahoma, 93,526 domestic. Well completion reports filed with the Oklahoma Water Resources Board, located by public land survey. Only aggregates are shown; owner names and addresses are never stored. Retrieved .
Oklahoma DEQ land sites: 238 regulated sites located in Oklahoma. Superfund sites, voluntary cleanup sites and solid waste facilities from the Oklahoma Department of Environmental Quality. Retrieved September 18, 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.