City of Denison Laboratory
4631 Randell Lake Road
Denison, TX 75020
- Total coliform & E. coli
Well water testing in Grayson County, Texas
Labs copied from the official Texas certified lab list (last verified 2026-10-26). All Texas labs
The official Texas list shows 2 certified labs in Grayson County. Call before you sample to confirm the lab accepts private well water and to ask about bottles, prices and drop-off times.
Certified labs in Grayson County
City of Sherman Utilities Laboratory
288 Post Oak Road
Sherman, TX 75090
- Total coliform & E. coli
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What to test for
- TCEQ says testing for total coliform and E. coli by an accredited lab is the first step to finding out whether your well is contaminated, for example after flooding, a loss of water pressure, or recurring digestive problems. Ask the lab for a sterile container and sampling form; results usually take two to three days. Source
- If total coliform is found, TCEQ says not to use the water for drinking, bathing, cooking or washing dishes. Boil or disinfect it, or use bottled water, disinfect the well, and retest until the lab reports total coliform absent. Source
After a flood in Grayson County
EPA says to test a private well for bacteria after flooding before drinking the water again. Check current flood alerts and Flood Watch, and read flood season testing. EPA: your well after a flood
Local help
Your Grayson County or local health department can tell you about local well testing, including any free or low-cost programs. State contact: TCEQ (help finding a drinking water lab).
Questions
Where can I test well water in Grayson County, TX?
The official Texas certified lab list shows 2 labs in Grayson County; they are listed on this page with phone numbers. Call first to confirm they accept private well samples.
How often should I test my well?
EPA recommends testing every year for total coliform bacteria, nitrates, total dissolved solids and pH, and testing right away after flooding, well repairs, or a change in taste, color or smell.
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