Manganese and arsenic are widespread in Washington County wells.
2 widespread, 2 rare out of 4 health checks.
From 34 wells tested in Washington County since 2005; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (4), lead (4).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
About 1 in 18 people 2,448 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Washington County compares with Mississippi and the counties around it.
Each result puts Washington County next to the 6 counties that border it, on the chart's 0 to 50% scale.
These 2 are widespread in Washington County wells.
Manganese29 of 32 wells over
Too few tested to show: Chicot, AR, Humphreys, Issaquena, Sharkey.
Arsenic2 of 11 wells over
Too few tested to show: Chicot, AR, Humphreys, Issaquena, Sharkey.
These 2 are rare in Washington County.
Nitrate1 of 27 wells over
Too few tested to show: Bolivar, Chicot, AR, Humphreys, Issaquena.
Fluoride0 of 24 wells over
Too few tested to show: Bolivar, Chicot, AR, Humphreys, Issaquena.
Too few Washington County wells were tested for these 2.
Uranium4 wells tested
Lead4 wells tested
Every well needs a bacteria test every year.
No bacteria tests from Washington County wells are in the public data. Test every year anyway.
Iron reached staining levels in 31 of 32 tested wells, and it isn't a health risk.
Iron stains31 of 32 wells had it
Too few tested to show: Chicot, AR, Humphreys, Issaquena, Sharkey.
Washington County has 34 tested wells, and the busiest decade for testing was the 2010s.
Only 1 of the 34 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Washington 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 Washington County.
- Bacteria
- Nitrate
- Manganese
- Arsenic
What Mississippi offers well owners
- Free testingWe didn't find a free program for all of Mississippi. Mississippi's private well page
- Certified labsMississippi's list of certified labs
- Well recordsWe didn't find an online search.
Half the household wells here are shallower than 450 feet.
That comes from 1,256 household wells in Mississippi's drilling records. Most wells of every kind here are 100 to 127 feet deep. Wells as deep as Washington County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 71 of the 81 other Mississippi counties with enough drilling records.
How to find your own well's depth
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Washington County.
Washington 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 4 town water systems in Washington County test for PFAS. None found any. No well in Washington 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 Washington County
Is well water in Washington County safe to drink?
29 of 32 wells tested in Washington County had manganese over the limit, about 9 in 10. Across Mississippi it's about 1 in 3. That's a bigger share than in 3 of the 4 other Mississippi counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated. So test your own well for manganese before you count on it.
Where can I get my well tested in Washington County?
Use a lab Mississippi has certified for drinking water. Mississippi's list is linked above, in the box about testing. Ask for bacteria, nitrate, manganese and arsenic, the tests that matter most in Washington County.
How deep are wells in Washington County?
Half the household wells here are shallower than 450 feet. Typical household wells here go deeper than in 71 of the 81 other Mississippi counties with enough drilling records.
How does Washington County compare with the counties around it?
For manganese, the share of tested wells over the limit: 1 of the 2 neighboring counties with data had a higher share than Washington County, at 91%. Sunflower had the most, at 100%. Groundwater doesn't stop at county lines, so Sunflower's 100% is worth knowing about if you live near it.
How often should I test my well in Washington County?
Washington County has no public bacteria results for wells, so follow the CDC's advice: 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 Washington County numbers come from
- People on wells: 2,448 in Washington County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 505 well water samples from 34 wells in the Water Quality Portal, run by the USGS and EPA, 2005 to 2020.
- Well depths: 1,256 Mississippi drilling records for Washington County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 6 counties that share a border with Washington County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 4 town water systems in Washington County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Washington County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: Mississippi State Department of Health, checked November 1, 2026.