Well water in Mississippi

Name: Private well water quality in Mississippi
Creator: Well Water Nerd
License: Public domain (US federal government data)

In Mississippi, 5% of 317 tested well samples exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.

22,129 test results across 14 contaminants from at least 3,412 wells, 1911 to 2022; iron has the most at 4,874. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 434,766 people in Mississippi get their drinking water from a private well, per USGS 2015 county water use.

Separately, the USGS national arsenic model estimates that <1% of the 434,766 people on private wells in Mississippi draw water above 10 ug/L, from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Mississippi. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.

Contaminant	Above limit	Samples	Detected	Median	Highest	Limit
Arsenic 1973 to 2022	5%	317	51%	0.03	103	10 ug/L EPA limit
Nitrate 1911 to 2022	1%	4,108	67%	0.023	81.3	10 mg/L EPA limit
Fluoride 1934 to 2022	<1%	3,836	91%	0.2	200	4 mg/L EPA limit
Radium (226 + 228) 1985 to 2019	<1%	276	80%	0.085	6.6	5 pCi/L EPA limit
Lead 1973 to 2022	0%	288	55%	0	12.5	15 ug/L EPA limit
Copper 1962 to 2022	0%	273	39%	0	0.31	1.3 mg/L EPA limit
Uranium 1955 to 2022	0%	242	32%	0	2.13	30 ug/L EPA limit
PFOA 2019 to 2022	0%	32	6%	0	2.6	4 ng/L EPA limit
PFOS 2019 to 2022	0%	32	0%	0	0	4 ng/L EPA limit
Iron 1911 to 2022	no limit	4,874	97%	180	320,000	300 ug/L nuisance level
Sodium 1911 to 2022	no limit	4,286	100%	39	120,000	20 mg/L health guideline
Manganese 1919 to 2022	no limit	2,327	94%	38.9	89,000	300 ug/L health guideline
Chloride 1911 to 2022	no limit	1,135	100%	6.4	2,500	250 mg/L nuisance level
Radon 1996 to 2014	no limit	103	100%	135	630	2,000 pCi/L health guideline

Over time

Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.

Contaminant	before 2000	2000s	2010s	2020s
Nitrate	<1%3,441 samples	3%309 samples	<1%329 samples	3%29 samples
Fluoride	<1%3,467 samples	0%173 samples	0%178 samples	0%18 samples
Arsenic	4%94 samples	3%40 samples	6%165 samples	0%18 samples
Lead	0%112 samples	0%40 samples	0%118 samples	0%18 samples
Radium (226 + 228)	0%93 samples	2%54 samples	0%129 samples	n/a
Copper	0%97 samples	0%40 samples	0%118 samples	0%18 samples

Nitrate, fluoride, arsenic, lead, radium (226 + 228), copper have held within a few points between the two most recent periods with enough samples.

What this means

The contaminants most often above their limit here are arsenic (5% of 317 samples), nitrate (1% of 4,108 samples), and fluoride (<1% of 3,836 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.

Iron, Manganese, and Chloride are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.

What to test for in Mississippi

1
Arsenic
5% of 317 local samples were above the limit.
2
Nitrate
1% of 4,108 local samples were above the limit.
3
Fluoride
<1% of 3,836 local samples were above the limit.
4
Radium (226 + 228)
<1% of 276 local samples were above the limit.
5
Coliform bacteria
Recommended for every private well, every year.
6
Radon
Median local reading is 135 pCi/L.
7
Chloride
Detected in 100% of local samples.

Test your Mississippi well for arsenic, nitrate and fluoride

Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.

Order the Tap Score well water test kit, from $209 Already tested? Upload the report

Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.

Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.

Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.

Where to get a well tested in Mississippi: certified labs, state programs and prices.

Already have results back? Get your lab report read against the Mississippi numbers, $29. Every line explained, ranked by what matters, with the fix for each.

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Send me the Mississippi report

The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.

The rock under Mississippi

Not a principal aquifer

The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.

Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the state centroid. A single well can sit in a different unit, especially near a boundary.

Official help in Mississippi

Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.

Private Wells, Mississippi State Department of Health
Water Supply Certification: In-State Participating Labs, Mississippi State Department of Health

Treatment that fits the local profile

Arsenic

Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Fluoride

Point-of-use reverse osmosis; Activated alumina; Distillation

Radium (226 + 228)

Water softener (cation exchange); Point-of-use reverse osmosis

Iron

Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration

Systems we would look at first

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For arsenic

Under-sink reverse osmosis system

under-sink or countertop, about $300

Look for NSF/ANSI 58 certification listing the contaminant you need removed.

For arsenic

Whole-house arsenic and uranium filter

whole-house, at the point of entry, about $2,500

Adsorptive iron-based media; sized to your well yield.

For arsenic

Aquasana SmartFlow reverse osmosis

under-sink or countertop, about $225

Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.

For iron

Iron and manganese oxidizing filter

whole-house, at the point of entry, about $1,800

Air-injection or greensand media; fixes staining at the source.

Common questions

Is there arsenic in well water in Mississippi?

Arsenic was detected in 51% of 317 public well samples in Mississippi, and 5% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.

How high is radon in well water in Mississippi?

The median radon level across 103 public samples in Mississippi was 135 pCi/L, with a high of 630 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Mississippi?

Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.

Counties in Mississippi

Want the numbers themselves? Download the Mississippi dataset as CSV, every county and town, with the sources named.

Sources

USGS Water Quality Portal: 22,129 samples in Mississippi. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
USGS national arsenic model (Ayotte 2017): estimated share of 434,766 people on private wells in Mississippi above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.

Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.