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Manganese in Oregon well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2000 to 2026Updated November 8, 2026

Manganese is widespread, over the limit in 15% or more of tested wells, in 14 of the 28 Oregon counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. A county's share tells you how likely a problem is nearby. Only a test of your own well tells you what's in it.

Find a manganese test See every county

How Oregon compares with the rest of the country

Across Oregon, about 2 in 10 tested wells had manganese over the EPA health advisory of 0.3 mg/L (337 of 1,741). Across all tested wells in the US it's about 1 in 7. So manganese turns up somewhat more often in Oregon than in the country as a whole. Check your county below.

Why it matters: High levels over many years may affect the nervous system, and babies are more sensitive to it. It also leaves black stains.

Manganese dissolves out of rock and soil, especially in water with little oxygen.

Manganese in tested wells, county by county

Share of each county's tested wells with at least one result over the EPA health advisory of 0.3 mg/L. Counties need 10 or more tested wells to be listed. Widespread means 15% or more, worth checking 5 to 15%, rare under 5%.

CountyWells testedWells over the limitLevel
Washington County 27
81% 22 of 27
 Widespread
Multnomah County 46
72% 33 of 46
 Widespread
Douglas County 58
52% 30 of 58
 Widespread
Coos County 30
50% 15 of 30
 Widespread
Curry County 12
50% 6 of 12
 Widespread
Lincoln County 23
48% 11 of 23
 Widespread
Marion County 77
47% 36 of 77
 Widespread
Yamhill County 69
46% 32 of 69
 Widespread
Union County 16
38% 6 of 16
 Widespread
Columbia County 14
36%* 5 of 14
 Widespread
Clackamas County 35
31% 11 of 35
 Widespread
Benton County 34
24% 8 of 34
 Widespread
Clatsop County 49
22% 11 of 49
 Widespread
Josephine County 37
19% 7 of 37
 Widespread
Linn County 52
17% 9 of 52
 Widespread
Polk County 22
14% 3 of 22
 Worth checking
Gilliam County 23
13% 3 of 23
 Worth checking
Deschutes County 141
12% 17 of 141
 Worth checking
Malheur County 46
11% 5 of 46
 Worth checking
Klamath County 107
9% 10 of 107
 Worth checking
Crook County 11
9%* 1 of 11
 Worth checking
Harney County 94
9% 8 of 94
 Worth checking
Lane County 88
8% 7 of 88
 Worth checking
Tillamook County 40
8% 3 of 40
 Worth checking
Morrow County 85
7% 6 of 85
 Worth checking
Jackson County 168
6% 10 of 168
 Worth checking
Umatilla County 279
5% 15 of 279
 Worth checking
Wasco County 34
3% 1 of 34
 Rare

* Likely overstated. These shares come from a narrow set of wells, so they probably run high for the county as a whole:

  • Columbia County: All of these tests come from Oregon's environment department in one small part of the county, so it may not match the rest of the county.
  • Crook County: All of these tests come from Oregon's environment department in one small part of the county, so it may not match the rest of the county.

8 more Oregon counties have 1 to 9 tested wells for manganese, too few to rate.

Download this table (CSV) ยท Free to reuse under CC BY 4.0

Where to get your well tested for manganese in Oregon

1

Your county health department

Oregon doesn't run a statewide free testing program that we know of. Some county health departments test wells or sell kits, so call yours first.

Oregon's private well page
2

A lab Oregon certifies

Ask for manganese by name. Results from a certified lab count for a home sale or a loan.

Labs certified by Oregon
3

A mail-in kit

Fill the bottles at your kitchen tap and mail them back. We mark the kits that include manganese.

Compare kits

Keep reading about wells in Oregon

Questions people ask about manganese in Oregon

Is there manganese in Oregon well water?

Manganese is widespread, over the limit in 15% or more of tested wells, in 14 of the 28 Oregon counties with 10 or more tested wells. 1 more look high, but those results likely overstate it. Across Oregon, about 2 in 10 tested wells had manganese over the EPA health advisory of 0.3 mg/L (337 of 1,741). Across all tested wells in the US it's about 1 in 7. So manganese turns up somewhat more often in Oregon than in the country as a whole. Check your county below.

Where can I get my well tested for manganese in Oregon?

Use a lab certified by Oregon for drinking water, or a mail-in kit that includes manganese from a certified lab. Some county health departments test wells too, so call yours first.

See Oregon's list of certified labs, or compare mail-in kits.

Where these numbers come from

  • Lab tests: Water Quality Portal (USGS and EPA), well samples since 2000. A well counts as over if any of its tests was over the EPA health advisory of 0.3 mg/L. Wells tested for studies and monitoring, not a random sample of homes.
  • Likely overstated: our own check of who tested the wells, when and where. How we check.
  • State programs and links: Oregon Health Authority.