Only 2 health checks had enough tested wells in St. Tammany Parish, and both came back rare.
Both health checks came back rare here.
From 65 wells tested in St. Tammany Parish since 2001; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: nitrate (3), arsenic (3), uranium (3), radon (3), lead (3).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 3 people 86,249 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 St. Tammany Parish compares with Louisiana and the counties around it.
Each result puts St. Tammany Parish next to the 8 counties that border it, on the chart's 0 to 50% scale.
Both health checks are rare in St. Tammany Parish.
Manganese0 of 18 wells over
Too few tested to show: Hancock, MS, Jefferson, Orleans, Pearl River, MS, St. Bernard, St. John the Baptist, Washington.
Fluoride0 of 58 wells over
Too few tested to show: Hancock, MS, Jefferson, Orleans, Pearl River, MS, St. Bernard, St. John the Baptist, Washington.
Too few St. Tammany Parish wells were tested for these 5.
Nitrate3 wells tested
Arsenic3 wells tested
Uranium3 wells tested
Radon in water3 wells tested
Lead3 wells tested
Coliform bacteria turned up in 4 of 8 tested St. Tammany Parish wells, so test for it every year.
Coliform bacteria4 of 8 wells had it
E. coli0 of 8 wells had it
E. coli means human or animal waste is getting in, so if a test of your St. Tammany Parish well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 0 of 18 tested wells, and it isn't a health risk.
Iron stains0 of 18 wells had it
Too few tested to show: Hancock, MS, Jefferson, Orleans, Pearl River, MS, St. Bernard, St. John the Baptist, Washington.
Most of the 65 wells tested in St. Tammany Parish were last tested before 2010.
An old result shows the water as it was then, so treat these 65 wells as a starting point and test your own.
Most St. Tammany Parish 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 3 things to check in St. Tammany Parish.
- Bacteria
- Nitrate
- Arsenic
What Louisiana offers well owners
- Free testingWe didn't find a free program for all of Louisiana. Louisiana's private well page
- Certified labsWe didn't find an online list.
- Well recordsLouisiana's well record search
Half the household wells here are shallower than 240 feet.
That comes from 17,988 household wells in Louisiana's drilling records. Most wells of every kind here are 120 to 400 feet deep. Wells as deep as St. Tammany Parish'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 46 of the 57 other Louisiana counties with enough drilling records.
Look up your own well's depth in Louisiana's well record search, or see how to find it.
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in St. Tammany Parish.
St. Tammany Parish 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 19 town water systems in St. Tammany Parish test for PFAS. 1 found some PFAS, all below the new limits. No well in St. Tammany Parish 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 St. Tammany Parish
Is well water in St. Tammany Parish safe to drink?
Most tested wells in St. Tammany Parish came in under the limits. Of 2 health checks with enough tests, manganese came closest, at 0 of 18 wells over. Every well is different, so test yours for bacteria, nitrate and arsenic.
Where can I get my well tested in St. Tammany Parish?
Use a lab Louisiana has certified for drinking water. Louisiana's list is linked above, in the box about testing. Ask for bacteria, nitrate and arsenic, the tests that matter most in St. Tammany Parish.
How deep are wells in St. Tammany Parish?
Half the household wells here are shallower than 240 feet. Typical household wells here go deeper than in 46 of the 57 other Louisiana counties with enough drilling records.
How does St. Tammany Parish compare with the counties around it?
For manganese, the share of tested wells over the limit: Tangipahoa, the one neighbor with data, came in higher than St. Tammany Parish, at 13% against 0%. Groundwater doesn't stop at county lines, so Tangipahoa's 13% is worth knowing about if you live near it.
How often should I test my well in St. Tammany Parish?
In St. Tammany Parish, 4 of 8 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 St. Tammany Parish numbers come from
- People on wells: 86,249 in St. Tammany Parish, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 146 well water samples from 65 wells in the Water Quality Portal, run by the USGS and EPA, 2001 to 2015.
- Well depths: 17,988 Louisiana drilling records for St. Tammany Parish, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with St. Tammany Parish, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 19 town water systems in St. Tammany Parish under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: St. Tammany Parish is zone 3 on the EPA Map of Radon Zones.
- State programs and links: Louisiana Department of Health, checked November 1, 2026.