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Manganese in Montana well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2000 to 2025Updated November 8, 2026

Manganese is widespread, over the limit in 15% or more of tested wells, in 8 of the 18 Montana counties with 10 or more tested wells. 4 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 Montana compares with the rest of the country

Across Montana, about 1 in 3 tested wells had manganese over the EPA health advisory of 0.3 mg/L (582 of 1,720). Across all tested wells in the US it's about 1 in 7. So manganese turns up in Montana wells about twice as often as in the country as a whole, and a test is worth adding even if your county isn't on the list 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
Deer Lodge County 11
64% 7 of 11
 Widespread
Silver Bow County 41
46% 19 of 41
 Widespread
Rosebud County 946
46%* 431 of 946
 Widespread
Powell County 63
44%* 28 of 63
 Widespread
Richland County 16
44% 7 of 16
 Widespread
Big Horn County 12
42% 5 of 12
 Widespread
Powder River County 73
41%* 30 of 73
 Widespread
Roosevelt County 66
29% 19 of 66
 Widespread
Jefferson County 58
22% 13 of 58
 Widespread
Yellowstone County 14
21% 3 of 14
 Widespread
Lewis and Clark County 27
19% 5 of 27
 Widespread
Flathead County 19
16%* 3 of 19
 Widespread
Glacier County 31
10% 3 of 31
 Worth checking
Gallatin County 209
0% 0 of 209
 Rare
Valley County 34
0% 0 of 34
 Rare
Ravalli County 22
0% 0 of 22
 Rare
Carbon County 14
0% 0 of 14
 Rare
Cascade County 11
0% 0 of 11
 Rare

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

  • Rosebud County: Almost all of these tests come from a single agency in one small part of the county, so it may not match the rest of the county.
  • Powell County: Most of these tests come from one small part of the county between 2000 and 2010, so this likely overstates it.
  • Powder River County: All of these tests come from a single agency in one small part of the county, so it may not match the rest of the county.
  • Flathead County: Most of these tests come from one small part of the county, mostly before 2013, so this likely overstates it.

18 more Montana counties have 1 to 9 tested wells for manganese, too few to rate.

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Where to get your well tested for manganese in Montana

1

Free testing, with limits

Montana's free well testing is only for childcare facilities. Check which tests it includes before you count on it for manganese.

Montana's private well page
2

A lab Montana certifies

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

Labs certified by Montana
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 Montana

Questions people ask about manganese in Montana

Is there manganese in Montana well water?

Manganese is widespread, over the limit in 15% or more of tested wells, in 8 of the 18 Montana counties with 10 or more tested wells. 4 more look high, but those results likely overstate it. Across Montana, about 1 in 3 tested wells had manganese over the EPA health advisory of 0.3 mg/L (582 of 1,720). Across all tested wells in the US it's about 1 in 7. So manganese turns up in Montana wells about twice as often as in the country as a whole, and a test is worth adding even if your county isn't on the list below.

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

Montana's free well testing is only for childcare facilities. If that doesn't cover you, use a lab certified by Montana for drinking water, or a mail-in kit that includes manganese from a certified lab.

See Montana'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: Department of Environmental Quality.