Well water in Oregon

Name: Private well water quality in Oregon
Creator: Well Water Nerd
License: Public domain (US federal government data)

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Testing strongly recommended

tested well samples in Oregon exceeded the EPA limit for E. coli (0 MPN/100mL), based on public data from USGS Water Quality Portal.

60,054 test results across 15 contaminants from at least 4,623 wells, 1902 to 2026; chloride has the most at 18,646. Data refreshed September 15, 2026.

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

An estimated 631,538 people in Oregon get their drinking water from a private well, per USGS 2015 county water use.

Separately, the USGS national arsenic model estimates that 4% of the 631,538 people on private wells in Oregon draw water above 10 ug/L (the model's range is 3% to 5%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Oregon. 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
E. coli 2006 to 2018	59%	49	59%	1	980	0 MPN/100mL EPA limit
Arsenic 1902 to 2026	39%	4,750	92%	7	1,260	10 ug/L EPA limit
Nitrate 1902 to 2025	17%	2,606	82%	0.52	215	10 mg/L EPA limit
Lead 1975 to 2026	10%	1,423	87%	0.78	4,430	15 ug/L EPA limit
Uranium 1993 to 2026	2%	1,269	91%	0.6	238	30 ug/L EPA limit
Fluoride 1903 to 2025	1%	2,674	95%	0.3	19	4 mg/L EPA limit
Copper 1969 to 2026	<1%	1,759	90%	0.006	7.5	1.3 mg/L EPA limit
Radium (226 + 228) 2004 to 2016	0%	60	53%	0.029	1.3	5 pCi/L EPA limit
Chloride 1903 to 2026	no limit	18,646	100%	12.1	15,900	250 mg/L nuisance level
Sodium 1903 to 2026	no limit	11,223	100%	28.4	9,400	20 mg/L health guideline
Iron 1945 to 2026	no limit	8,259	96%	250	4,800,000	300 ug/L nuisance level
Manganese 1951 to 2026	no limit	7,247	94%	100	111,000	300 ug/L health guideline
Radon 1991 to 2016	no limit	83	98%	390	11,600	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: PFOA (3), PFOS (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
Arsenic	37%2,754 samples	57%818 samples	38%801 samples	12%377 samples
Fluoride	<1%2,008 samples	3%247 samples	1%309 samples	0%110 samples
Nitrate	18%2,032 samples	16%276 samples	5%288 samples	0%10 samples
Copper	<1%870 samples	0%531 samples	0%290 samples	0%68 samples
Lead	21%473 samples	11%215 samples	3%599 samples	1%136 samples
Uranium	0%79 samples	2%357 samples	2%614 samples	5%219 samples

Arsenic above the limit in Oregon fell from 38% of 801 samples in the 2010s to 12% of 377 in the 2020s.

Nitrate above the limit in Oregon fell from 16% of 276 samples in the 2000s to 5% of 288 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 e. coli (59% of 49 samples), arsenic (39% of 4,750 samples), and nitrate (17% of 2,606 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 Oregon

1
E. coli
59% of 49 local samples were above the limit.
2
Arsenic
39% of 4,750 local samples were above the limit.
3
Nitrate
17% of 2,606 local samples were above the limit.
4
Lead
10% of 1,423 local samples were above the limit.
5
Uranium
2% of 1,269 local samples were above the limit.
6
Fluoride
1% of 2,674 local samples were above the limit.
7
Copper
<1% of 1,759 local samples were above the limit.

Test your Oregon well for E. coli, arsenic 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 Oregon: certified labs, state programs and prices.

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

Free, one email

Send me the Oregon report

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

The rock under Oregon

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 Oregon

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.

Domestic Well Safety, Oregon Health Authority
Oregon Environmental Laboratory Accreditation Program, Oregon Health Authority

Contamination sources on record in Oregon

Oregon DEQ active tank sites records 1,199 regulated sites in Oregon, among 1,199 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.

1,199: registered underground storage tank sitesRegistered tanks are regulated and inspected; they matter most when they are old or near a shallow well.

Treatment that fits the local profile

E. coli

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

Arsenic

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

Nitrate

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

Lead

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

Uranium

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

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 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 E. coli

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 arsenic

Under-sink reverse osmosis system

under-sink or countertop, about $300

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

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 arsenic

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 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

Is there arsenic in well water in Oregon?

Arsenic was detected in 92% of 4,750 public well samples in Oregon, and 39% 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 Oregon?

The median radon level across 83 public samples in Oregon was 390 pCi/L, with a high of 11,600 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Oregon?

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 Oregon

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

Sources

USGS Water Quality Portal: 60,054 samples in Oregon. 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 631,538 people on private wells in Oregon 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.
Oregon DEQ active tank sites: 1,199 regulated sites located in Oregon. Active underground storage tank sites from the Oregon 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.