Well water in Madison County, Texas
In Madison County, none of 53 tested well samples exceeded the EPA limit for fluoride, based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
The strongest signal is coliform bacteria: Recommended for every private well, every year, too few samples to carry the headline but first on the test list below.
345 test results across 14 contaminants from at least 17 wells, 1961 to 2026; fluoride has the most at 53. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
TWDB samples an ambient monitoring network of wells on a rotation, so these describe aquifers, not a survey of homeowners' tests.
An estimated 6,738 people in Madison County get their drinking water from a private well, per USGS 2015 county water use. That is about 48% of residents.
Separately, the USGS national arsenic model estimates that 3% of the 6,738 people on private wells in Madison County draw water above 10 ug/L (the model's range is 3% to 5%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Madison County. 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 |
|---|---|---|---|---|---|---|
| Fluoride 1961 to 2026 | 53 | 83% | 0.1 | 2 | 4 mg/L EPA limit | |
| Nitrate 1993 to 2026 | 24 | 67% | 0.082 | 0.455 | 10 mg/L EPA limit | |
| Arsenic 1993 to 2026 | 23 | 4% | 0 | 1.69 | 10 ug/L EPA limit | |
| Copper 1993 to 2026 | 23 | 43% | 0 | 0.006 | 1.3 mg/L EPA limit | |
| Lead 1993 to 2026 | 23 | 13% | 0 | 1.4 | 15 ug/L EPA limit | |
| Sodium 1961 to 2026 | no limit | 53 | 100% | 100 | 439 | 20 mg/L health guideline |
| Chloride 1961 to 2026 | no limit | 53 | 100% | 30 | 332 | 250 mg/L nuisance level |
| Iron 1976 to 2026 | no limit | 38 | 61% | 23.5 | 1,100 | 300 ug/L nuisance level |
| Manganese 1977 to 2026 | no limit | 32 | 72% | 5.11 | 70 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Uranium (8), Gross alpha (7), Radium (226 + 228) (6), E. coli (1), Radon (1).
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
Among contaminants with a federal limit, no tested sample in Madison County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
Chloride, Iron, and Manganese 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 Madison County
- 1Coliform bacteriaRecommended for every private well, every year.
- 2RadonMedian local reading is 72 pCi/L.
- 3NitrateRecommended for every private well, especially near farms or septic systems.
- 4ChlorideDetected in 100% of local samples.
- 5FluorideDetected in 83% of local samples.
- 6ManganeseDetected in 72% of local samples.
- 7IronDetected in 61% of local samples.
- 8Volatile organic compounds (VOCs)26 leaking underground storage tank sites on record locally.
Test your Madison County well for coliform bacteria, radon and nitrate
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 $209Already 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 Texas: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Madison County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Madison County
Texas coastal uplands aquifer system
Semiconsolidated sand. Coastal plain sands like these give steady yields at moderate depth. Salt water and sodium are the usual issues near the coast, and nitrate where the water table is shallow; arsenic and radon from bedrock are less common.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in Texas
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, Texas Groundwater Protection Committee
- Environmental Laboratory (NELAP) Accreditation, TCEQ
Contamination sources on record in Madison County
TCEQ records 26 leaking underground storage tank sites in Madison County, among 30 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 26
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 4
- lined landfills and transfer facilities
Free, no obligation
Get on the list for a free in-home water test in Madison County
No water treatment company serves Madison County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for Madison County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Madison County?
Arsenic was detected in 4% of 23 public well samples in Madison County, and 0% 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 often should I test a private well in Madison County?
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 near Madison County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the Texas dataset as CSV, every county and town, with the sources named.
Sources
- Texas Water Development Board Groundwater Database: 330 samples in Madison County. Water quality samples from the Texas Water Development Board Groundwater Database, collected by TWDB, groundwater conservation districts and cooperators. Retrieved September 9, 2026.
- USGS Water Quality Portal: 15 samples in Madison County. 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 6,738 people on private wells in Madison County 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.
- TCEQ regulated sites: 30 regulated sites located in Madison County. Leaking petroleum storage tank sites, state Superfund sites and municipal solid waste landfills from the Texas Commission on Environmental Quality. Retrieved September 9, 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.