Manganese is widespread in District of Columbia County wells.
1 widespread, 5 rare out of 6 health checks.
From 51 wells tested in District of Columbia County since 2002; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: radon (3).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Radon risk (a gas from rock)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how District of Columbia County compares with District of Columbia and the counties around it.
Each result puts District of Columbia County next to the 4 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in District of Columbia County wells.
Manganese19 of 38 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
These 5 are rare in District of Columbia County.
Arsenic2 of 44 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
Nitrate1 of 38 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
Uranium0 of 31 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
Lead0 of 31 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
Fluoride0 of 38 wells over
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
Too few District of Columbia County wells were tested for this one.
Radon in water3 wells tested
Coliform bacteria turned up in 2 of 2 tested District of Columbia County wells, so test for it every year.
Coliform bacteria2 of 2 wells had it
E. coli2 of 2 wells had it
E. coli means human or animal waste is getting in, so if a test of your District of Columbia County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 20 of 38 tested wells, and it isn't a health risk.
Iron stains20 of 38 wells had it
Too few tested to show: Alexandria city, VA, Arlington, VA, Prince George's, MD.
District of Columbia County has 51 tested wells, and the busiest decade for testing was the 2010s.
Only 9 of the 51 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most District of Columbia County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 4 things to check in District of Columbia County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What District of Columbia offers well owners
- Free testingWe didn't find a free program for all of District of Columbia.
- Certified labsWe didn't find an online list.
- Well recordsWe didn't find an online search.
Here's what we know about radon and PFAS in District of Columbia County.
District of Columbia County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide
Between 2023 and 2025 the EPA had 3 town water systems in District of Columbia County test for PFAS. 3 found some PFAS, all below the new limits. No well in District of Columbia County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in District of Columbia County
Is well water in District of Columbia County safe to drink?
19 of 38 wells tested in District of Columbia County had manganese over the limit, about 5 in 10. Across District of Columbia it's about 5 in 10. So test your own well for manganese before you count on it.
Where can I get my well tested in District of Columbia County?
Use a lab District of Columbia has certified for drinking water. District of Columbia's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in District of Columbia County.
How does District of Columbia County compare with the counties around it?
For manganese, the share of tested wells over the limit: Montgomery, MD, the one neighbor with data, came in lower than District of Columbia County, at 20% against 50%. Groundwater doesn't stop at county lines, so Montgomery, MD's 20% is worth knowing about if you live near it.
How often should I test my well in District of Columbia County?
In District of Columbia County, 2 of 2 tested wells had coliform bacteria, so the CDC's advice matters here: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the District of Columbia County numbers come from
- Lab tests: 517 well water samples from 51 wells in the Water Quality Portal, run by the USGS and EPA, 2002 to 2021.
- Neighboring counties: the 4 counties that share a border with District of Columbia County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 3 town water systems in District of Columbia County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: District of Columbia County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: Department of Energy and Environment, checked November 1, 2026.