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Manganese in Maryland well water, by county

By the Tested Water teamLab data from the USGS and EPA Water Quality Portal, 2000 to 2023Updated November 8, 2026

Manganese is widespread, over the limit in 15% or more of tested wells, in 5 of the 18 Maryland counties with 10 or more tested wells. 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 Maryland compares with the rest of the country

Across Maryland, about 2 in 10 tested wells had manganese over the EPA health advisory of 0.3 mg/L (111 of 712). Across all tested wells in the US it's about 1 in 7. Maryland is about average, so the county you live in tells you more than the state does.

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
Cecil County 66
56% 37 of 66
 Widespread
Dorchester County 41
27% 11 of 41
 Widespread
Garrett County 70
23% 16 of 70
 Widespread
Montgomery County 30
20% 6 of 30
 Widespread
Carroll County 11
18% 2 of 11
 Widespread
Baltimore County 123
14% 17 of 123
 Worth checking
Wicomico County 16
12% 2 of 16
 Worth checking
Worcester County 52
10% 5 of 52
 Worth checking
Anne Arundel County 47
9% 4 of 47
 Worth checking
Charles County 19
5% 1 of 19
 Worth checking
Frederick County 20
5% 1 of 20
 Worth checking
Kent County 47
4% 2 of 47
 Rare
Queen Anne's County 45
0% 0 of 45
 Rare
Caroline County 27
0% 0 of 27
 Rare
St. Mary's County 24
0% 0 of 24
 Rare
Washington County 15
0% 0 of 15
 Rare
Talbot County 12
0% 0 of 12
 Rare
Calvert County 10
0% 0 of 10
 Rare

5 more Maryland 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 Maryland

1

Your county health department

Maryland 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.

Maryland's private well page
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 Maryland

Questions people ask about manganese in Maryland

Is there manganese in Maryland well water?

Manganese is widespread, over the limit in 15% or more of tested wells, in 5 of the 18 Maryland counties with 10 or more tested wells. Across Maryland, about 2 in 10 tested wells had manganese over the EPA health advisory of 0.3 mg/L (111 of 712). Across all tested wells in the US it's about 1 in 7. Maryland is about average, so the county you live in tells you more than the state does.

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

Use a lab certified by Maryland 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 Maryland's list of certified labs (a PDF list), 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: Maryland Department of the Environment.