Well water in Comal County, Texas
In Comal County, 2% of 58 tested well samples exceeded the EPA limit for nitrate (10 mg/L), based on public data from Texas Water Development Board Groundwater Database and USGS Water Quality Portal.
123 individual samples from 70 wells, 1936 to 2023. 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 Comal 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 | |
|---|---|---|---|---|---|---|---|
| Nitrate 1936 to 2023 | 58 | 90% | 2% | 1.67 | 21.4 | 10 mg/L EPA limit | |
| Uranium 1996 to 2023 | 114 | 71% | 0% | 0.683 | 2.2 | 30 ug/L EPA limit | |
| Fluoride 1969 to 2023 | 81 | 93% | 0% | 0.2 | 3.1 | 4 mg/L EPA limit | |
| Arsenic 1974 to 2023 | 56 | 14% | 0% | 0 | 1.3 | 10 ug/L EPA limit | |
| Copper 1969 to 2023 | 50 | 70% | 0% | 0.002 | 0.01 | 1.3 mg/L EPA limit | |
| Lead 1975 to 2023 | 43 | 26% | 0% | 0 | 7 | 15 ug/L EPA limit | |
| Radium (226 + 228) 1994 to 2018 | 30 | 67% | 0% | 0.127 | 0.8 | 5 pCi/L EPA limit | |
| Chloride 1936 to 2023 | 123 | 100% | no limit | 13.4 | 840 | 250 mg/L nuisance level | |
| Sodium 1936 to 2023 | 98 | 100% | no limit | 7.13 | 402 | 20 mg/L health guideline | |
| Manganese 1969 to 2023 | 56 | 23% | no limit | 0 | 19.2 | 300 ug/L health guideline | |
| Iron 1969 to 2023 | 53 | 28% | no limit | 0 | 1,450 | 300 ug/L nuisance level | |
| Radon 1996 to 2017 | 31 | 94% | no limit | 350 | 780 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: PFOS (2), E. coli (6), Gross alpha (3), PFOA (2).
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What this means
The contaminants most often above their limit here are nitrate (2% of 58 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 Comal County
- Volatile organic compounds (VOCs)110 leaking underground storage tank sites on record locally.
- Nitrate2% of 58 local samples were above the limit.
- RadonMedian local reading is 350 pCi/L.
- PFOSAbove the limit in 1 of 2 local samples; too few to quote a rate.
- E. coliAbove the limit in 1 of 6 local samples; too few to quote a rate.
- ChlorideDetected in 100% of local samples.
- FluorideDetected in 93% of local samples.
- CopperDetected in 70% of local samples.
Contamination sources on record in Comal County
TCEQ records 110 leaking underground storage tank sites in Comal County, among 114 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.
- 110
- 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
Treatment that fits the local profile
- 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
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Comal 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 Comal County.
Common questions
Is there arsenic in well water in Comal County?
Arsenic was detected in 14% of 56 public well samples in Comal 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 Comal County?
The median radon level across 31 public samples in Comal County was 350 pCi/L, with a high of 780 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Comal 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: 626 samples in Comal 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: 180 samples in Comal 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: 114 regulated sites located in Comal 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.