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Private wells · by county

Texas well water by county: arsenic and nitrate

Modelled arsenic and nitrate for private-well users in every Texas county, what to test for, and where to find a certified lab. Private wells aren’t covered by the Safe Drinking Water Act.

See the countiesFind a certified lab
Texas counties

All 254 counties

Each mark = 1 in 100 well users the model places above 10 µg/L arsenic (scale 0–10)10 mg/L nitrate: the federal limit (MCL) for public systems

What the model can and can’t tell you
  • These figures describe the area, not your well. Only a lab test shows what’s in your water.
  • CDC says the Well Water Index figures “do not describe risk to individual wells.” (CDC Tracking Network)
  • The arsenic model is better at spotting low-arsenic areas than at confirming high ones.
  • Well-user counts are 2010 USGS estimates; tract values are averages over each census tract.
What to test your well for
  • Total coliform bacteriaEvery year
  • NitrateEvery year
  • Total dissolved solidsEvery year
  • pHEvery year
  • ArsenicAsk your local health department

EPA: Private Drinking Water Wells · CDC: Guidelines for Testing Well Water

Where to test in Texas

Use a state-certified lab

Texas Commission on Environmental Quality lists the laboratories certified to test drinking water in Texas.

Find a certified lab in Texas ↗EPA list of state programs ↗
Commercial · test your own well

Screening tells you if something is worth a closer look

A lab result is the number you can act on.

As an Amazon Associate, PurityMap earns from qualifying purchases. Affiliate disclosure

  • Lab-certified results

    ETR Labs Basic Water Quality Test Kit

    ETR Laboratories

    50+ substances, including lead, copper, arsenic, nitrate, hardness and coliform bacteria

    What it can't tell you: It does not test PFAS, and not every result on the panel falls under the lab's accredited scope.

    Check price on Amazon

  • Screening: quick check, not lab-grade

    Watersafe Drinking Water Test Kit

    Silver Lake Research

    Lead, bacteria, nitrate, copper, iron, chlorine, hardness and pH

    • Turnaround: Minutes; the bacteria test can take up to 48 hours

    What it can't tell you: Each test gives a yes/no or a rough range, not a lab number, and it cannot detect PFAS or arsenic.

    Check price on Amazon

A mail-in kit’s lab is accredited (ISO/IEC 17025) but may not be certified by your state. For a home sale, a loan, or a health-department follow-up, use a state-certified lab.

Questions

Texas well water

Sources: CDC Well Water Index (2024) · USGS arsenic and nitrate models · USGS domestic well populations · EPA and CDC testing guidance. Data last updated 2026-10-08. All sources →

How many people use private wells in Texas?

About 1.7 million people across 254 Texas counties, by the USGS 2010 estimate. USGS models place about 107,200 of them in areas where wells are likely to be above the 10 µg/L arsenic limit. These are area estimates, not well results.

Are private wells regulated in Texas?

The quality and safety of drinking water from private domestic wells are not regulated by the Federal Government under the Safe Drinking Water Act nor by most state governments and laws. (EPA) Testing and treatment are the owner's responsibility.

Where can I get my well tested in Texas?

Texas Commission on Environmental Quality keeps the list of laboratories certified to test drinking water in Texas. Only use laboratories that are certified to do drinking water testing. (EPA)