Well water in Kendall County, Texas
In Kendall County, 5% of 42 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.
663 test results across 13 contaminants from at least 129 wells, 1940 to 2011; sodium has the most at 158. 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 17,125 people in Kendall County get their drinking water from a private well, per USGS 2015 county water use. That is about 42% of residents.
Separately, the USGS national arsenic model estimates that <1% of the 17,125 people on private wells in Kendall County draw water above 10 ug/L, from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Kendall 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 |
|---|---|---|---|---|---|---|
| Nitrate 1990 to 2011 | 42 | 60% | 0.051 | 48.2 | 10 mg/L EPA limit | |
| Radium (226 + 228) 1994 to 2011 | 22 | 73% | 0.7 | 5.3 | 5 pCi/L EPA limit | |
| Fluoride 1940 to 2011 | 122 | 99% | 1.4 | 5.1 | 4 mg/L EPA limit | |
| Arsenic 1990 to 2011 | 33 | 18% | 0 | 2 | 10 ug/L EPA limit | |
| Copper 1994 to 2011 | 23 | 35% | 0 | 0.008 | 1.3 mg/L EPA limit | |
| Lead 1994 to 2011 | 19 | 26% | 0 | 3.4 | 15 ug/L EPA limit | |
| Gross alpha 1994 to 2011 | 11 | 45% | 0 | 6.2 | 15 pCi/L EPA limit | |
| Uranium 1996 to 2011 | 11 | 27% | 0 | 2 | 30 ug/L EPA limit | |
| Sodium 1940 to 2011 | no limit | 158 | 99% | 31.5 | 449 | 20 mg/L health guideline |
| Chloride 1940 to 2011 | no limit | 149 | 100% | 37 | 487 | 250 mg/L nuisance level |
| Iron 1966 to 2011 | no limit | 34 | 85% | 74.9 | 3,400 | 300 ug/L nuisance level |
| Manganese 1994 to 2011 | no limit | 28 | 82% | 3.52 | 19.5 | 300 ug/L health guideline |
| Radon 1990 to 1996 | no limit | 11 | 91% | 360 | 560 | 2,000 pCi/L health guideline |
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
The contaminants most often above their limit here are nitrate (5% of 42 samples), radium (226 + 228) (5% of 22 samples), and fluoride (2% of 122 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 Kendall County
- 1Nitrate5% of 42 local samples were above the limit.
- 2Radium (226 + 228)5% of 22 local samples were above the limit.
- 3Fluoride2% of 122 local samples were above the limit.
- 4Coliform bacteriaRecommended for every private well, every year.
- 5RadonMedian local reading is 360 pCi/L.
- 6ChlorideDetected in 100% of local samples.
- 7IronDetected in 85% of local samples.
- 8Volatile organic compounds (VOCs)22 leaking underground storage tank sites on record locally.
Test your Kendall County well for nitrate, radium (226 + 228) and fluoride
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 Kendall County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under Kendall County
Edwards-Trinity aquifer system
Sandstone and carbonate-rock. Layered sandstone and limestone means a well may draw from either. Hardness and iron are routine, and the limestone layers can carry bacteria and nitrate from the surface quickly, so test for both yearly.
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 Kendall County
TCEQ records 22 leaking underground storage tank sites in Kendall County, among 27 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.
- 22
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 5
- lined landfills and transfer facilities
Treatment that fits the local profile
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Iron
Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For nitrate
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For nitrate
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For iron
Iron and manganese oxidizing filter
whole-house, at the point of entry, about $1,800
Air-injection or greensand media; fixes staining at the source.
Free, no obligation
Get on the list for a free in-home water test in Kendall County
No water treatment company serves Kendall 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 Kendall County, and you get an email naming it first.
Common questions
Is there arsenic in well water in Kendall County?
Arsenic was detected in 18% of 33 public well samples in Kendall 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 Kendall County?
The median radon level across 11 public samples in Kendall County was 360 pCi/L, with a high of 560 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Kendall 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 Kendall 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: 564 samples in Kendall 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: 99 samples in Kendall 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 17,125 people on private wells in Kendall 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: 27 regulated sites located in Kendall 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.