Well water in Harris County, Texas
In Harris County, 2% of 322 tested well samples exceeded the EPA limit for uranium (30 ug/L), based on public data from USGS Water Quality Portal and Texas Water Development Board Groundwater Database.
322 individual samples from 167 wells, 1933 to 2025. 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. In that targeted sampling, 22% of 27 PFOS results in Harris County were above the EPA limit of 4 ng/L. In that targeted sampling, 19% of 27 PFOA results in Harris County were above the EPA limit of 4 ng/L.
What individual samples found
Each row summarizes every public sample for that contaminant inside Harris 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 | |
|---|---|---|---|---|---|---|---|
| PFOS 2024 to 2025 | 27 | 48% | 22% | 0 | 170 | 4 ng/L EPA limit | |
| PFOA 2024 to 2025 | 27 | 26% | 19% | 0 | 670 | 4 ng/L EPA limit | |
| E. coli 2002 to 2014 | 28 | 4% | 4% | 0 | 2 | 0 MPN/100mL EPA limit | |
| Uranium 1984 to 2025 | 322 | 97% | 2% | 1.47 | 44.5 | 30 ug/L EPA limit | |
| Radium (226 + 228) 1984 to 2016 | 277 | 96% | 0% | 0.62 | 4.9 | 5 pCi/L EPA limit | |
| Fluoride 1939 to 2014 | 33 | 100% | 0% | 0.2 | 1.4 | 4 mg/L EPA limit | |
| Arsenic 1984 to 2013 | 16 | 63% | 0% | 0.9 | 7.4 | 10 ug/L EPA limit | |
| Radon 2002 to 2016 | 86 | 100% | no limit | 635 | 2,510 | 2,000 pCi/L health guideline | |
| Chloride 1933 to 2013 | 66 | 100% | no limit | 39.7 | 459 | 250 mg/L nuisance level | |
| Sodium 1933 to 2013 | 53 | 100% | no limit | 50 | 289 | 20 mg/L health guideline | |
| Iron 1933 to 2009 | 29 | 79% | no limit | 100 | 9,500 | 300 ug/L nuisance level | |
| Manganese 1965 to 2015 | 17 | 76% | no limit | 0 | 100 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Copper (9), Lead (9), Nitrate (8), Gross alpha (2).
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What this means
The contaminants most often above their limit here are pfos (22% of 27 samples), pfoa (19% of 27 samples), and e. coli (4% of 28 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, 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 Harris County
- Volatile organic compounds (VOCs)4,278 leaking underground storage tank sites on record locally.
- Metals panel25 hazardous waste sites on record locally.
- PFOS22% of 27 local samples were above the limit.
- PFOA19% of 27 local samples were above the limit.
- E. coli4% of 28 local samples were above the limit.
- Uranium2% of 322 local samples were above the limit.
- RadonMedian local reading is 635 pCi/L.
- FluorideDetected in 100% of local samples.
- ChlorideDetected in 100% of local samples.
Contamination sources on record in Harris County
TCEQ records 4,278 leaking underground storage tank sites and 25 hazardous waste sites in Harris County, among 4,514 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.
- 4,278
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 25
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 211
- lined landfills and transfer facilities
Treatment that fits the local profile
- PFOS
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
- PFOA
- Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
- E. coli
- Shock chlorination and fix the well cap or casing; UV disinfection whole-house; Chlorination system
- Uranium
- Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
Get your Harris 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 Harris County.
Common questions
Is there arsenic in well water in Harris County?
Arsenic was detected in 63% of 16 public well samples in Harris 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 Harris County?
The median radon level across 86 public samples in Harris County was 635 pCi/L, with a high of 2,510 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Harris 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
- USGS Water Quality Portal: 811 samples in Harris 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.
- Texas Water Development Board Groundwater Database: 198 samples in Harris County. Water quality samples from the Texas Water Development Board Groundwater Database, collected by TWDB, groundwater conservation districts and cooperators. Retrieved September 9, 2026.
- TCEQ regulated sites: 4,514 regulated sites located in Harris 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.