Well water in Gonzales County, Texas
In Gonzales County, none of 124 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.
171 individual samples from 91 wells, 1928 to 2021. 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 Gonzales 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 | |
|---|---|---|---|---|---|---|---|
| Fluoride 1928 to 2021 | 124 | 92% | 0% | 0.245 | 2.55 | 4 mg/L EPA limit | |
| Nitrate 1963 to 2021 | 58 | 41% | 0% | 0 | 9.66 | 10 mg/L EPA limit | |
| Arsenic 1988 to 2014 | 50 | 16% | 0% | 0 | 4.98 | 10 ug/L EPA limit | |
| Lead 1988 to 2014 | 50 | 8% | 0% | 0 | 7.9 | 15 ug/L EPA limit | |
| Copper 1988 to 2014 | 50 | 62% | 0% | 0.003 | 0.034 | 1.3 mg/L EPA limit | |
| Uranium 2008 to 2016 | 10 | 0% | 0% | 0 | 0 | 30 ug/L EPA limit | |
| Chloride 1928 to 2021 | 171 | 100% | no limit | 104 | 5,823 | 250 mg/L nuisance level | |
| Sodium 1928 to 2021 | 171 | 100% | no limit | 112 | 4,078 | 20 mg/L health guideline | |
| Iron 1962 to 2014 | 72 | 64% | no limit | 36.5 | 15,000 | 300 ug/L nuisance level | |
| Manganese 1988 to 2014 | 50 | 84% | no limit | 11.5 | 960 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Gross alpha (8), Radium (226 + 228) (6), E. coli (2), Radon (2).
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What this means
Among contaminants with a federal limit, no tested sample in Gonzales 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 Gonzales County
- Volatile organic compounds (VOCs)43 leaking underground storage tank sites on record locally.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 108 pCi/L.
- ChlorideDetected in 100% of local samples.
- NitrateRecommended for every private well, especially near farms or septic systems.
- FluorideDetected in 92% of local samples.
- ManganeseDetected in 84% of local samples.
- IronDetected in 64% of local samples.
Contamination sources on record in Gonzales County
TCEQ records 43 leaking underground storage tank sites in Gonzales County, among 50 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.
- 43
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 7
- lined landfills and transfer facilities
Treatment that fits the local profile
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Copper
- Neutralizing filter to raise pH; Point-of-use reverse osmosis
- Chloride
- Point-of-use reverse osmosis; Distillation
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Get your Gonzales 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 Gonzales County.
Common questions
Is there arsenic in well water in Gonzales County?
Arsenic was detected in 16% of 50 public well samples in Gonzales 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 Gonzales County?
The median radon level across 2 public samples in Gonzales County was 108 pCi/L, with a high of 130 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Gonzales 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: 805 samples in Gonzales 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: 19 samples in Gonzales 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: 50 regulated sites located in Gonzales 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.