Well water in Medina County, Texas
In Medina County, 3% of 60 tested well samples exceeded the EPA limit for radium (226 + 228) (5 pCi/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
171 individual samples from 101 wells, 1930 to 2026. Data refreshed September 9, 2026.
TWDB samples an ambient monitoring network of wells on a rotation, so these describe aquifers, not a survey of homeowners' tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Medina 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 | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| E. coli 2008 to 2018 | 16 | 6% | 6% | 0 | 5 | 0 MPN/100mL EPA limit | |
| Radium (226 + 228) 1990 to 2018 | 60 | 82% | 3% | 0.31 | 10.7 | 5 pCi/L EPA limit | |
| Nitrate 1950 to 2026 | 91 | 93% | 2% | 0.973 | 39 | 10 mg/L EPA limit | |
| Fluoride 1930 to 2026 | 122 | 93% | <1% | 0.2 | 5.9 | 4 mg/L EPA limit | |
| Arsenic 1975 to 2026 | 92 | 13% | 0% | 0 | 2 | 10 ug/L EPA limit | |
| Uranium 1996 to 2026 | 85 | 62% | 0% | 0.619 | 5.31 | 30 ug/L EPA limit | |
| Copper 1975 to 2026 | 81 | 70% | 0% | 0.002 | 0.048 | 1.3 mg/L EPA limit | |
| Lead 1975 to 2026 | 79 | 23% | 0% | 0 | 7.1 | 15 ug/L EPA limit | |
| Chloride 1930 to 2026 | 171 | 99% | no limit | 14 | 5,500 | 250 mg/L nuisance level | |
| Sodium 1930 to 2026 | 169 | 100% | no limit | 8.4 | 2,080 | 20 mg/L health guideline | |
| Iron 1930 to 2026 | 97 | 36% | no limit | 0 | 5,271 | 300 ug/L nuisance level | |
| Manganese 1972 to 2026 | 84 | 32% | no limit | 0 | 258 | 300 ug/L health guideline | |
| Radon 1996 to 2017 | 36 | 64% | no limit | 105 | 2,010 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: Gross alpha (7), PFOA (8), PFOS (8).
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What this means
The contaminants most often above their limit here are e. coli (6% of 16 samples), radium (226 + 228) (3% of 60 samples), and nitrate (2% of 91 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.
Chloride is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Medina County
- Volatile organic compounds (VOCs)51 leaking underground storage tank sites on record locally.
- E. coli6% of 16 local samples were above the limit.
- Radium (226 + 228)3% of 60 local samples were above the limit.
- Nitrate2% of 91 local samples were above the limit.
- Fluoride<1% of 122 local samples were above the limit.
- RadonMedian local reading is 105 pCi/L.
- Gross alphaAbove the limit in 1 of 7 local samples; too few to quote a rate.
- ChlorideDetected in 99% of local samples.
Contamination sources on record in Medina County
TCEQ records 51 leaking underground storage tank sites in Medina County, among 60 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.
- 51
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 9
- lined landfills and transfer facilities
Treatment that fits the local profile
- E. coli
- Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
- Radium (226 + 228)
- Water softener (cation exchange); Point-of-use reverse osmosis
- Nitrate
- Point-of-use reverse osmosis; Anion exchange; Distillation
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
Get your Medina County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Medina County.
Common questions
Is there arsenic in well water in Medina County?
Arsenic was detected in 13% of 92 public well samples in Medina 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 high is radon in well water in Medina County?
The median radon level across 36 public samples in Medina County was 105 pCi/L, with a high of 2,010 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Medina 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.
Sources
- Texas Water Development Board Groundwater Database: 972 samples in Medina 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: 234 samples in Medina 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.
- TCEQ regulated sites: 60 regulated sites located in Medina 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.