Harris County, TX
These figures come from wells tested in Harris County, TX, not from any one well.
- Manganese is common in wells in Harris County, TX (16 of 150 tested wells were over that level), so it's worth testing for.
- Iron and sulfate are not common in wells in Harris County, TX (8 of 164 and 1 of 314 tested wells were over). Only a test tells you about your own well.
- Wells in Harris County, TX are typically hard (251 wells tested).
- Only a test of your own well tells you about your water.
What to test for
Start with the four this site covers:
- manganese (common in wells here)
- iron
- hardness
- sulfate
Most well owners also test for these. We point to the source and don't interpret the results.
- arsenic: occurs naturally in groundwater in many regions. USGS: arsenic and drinking water
- nitrate: common near farmland and septic systems. EPA: private drinking water wells
- total coliform bacteria: the standard yearly well check. EPA: private drinking water wells
- lead and copper: from household plumbing, especially when pH is below 6.5. EPA: lead in drinking water
- PFAS: several states run private-well sampling programs. EPA: PFAS
- a certified lab: states certify labs and some run their own private-well programs. Texas's certified-lab list (from your state drinking-water program)
The numbers
County figures describe the wells sampled there, not any one well. Exact counts, sample years and sources are below.
Iron Recent
| Level it's compared with | 0.3 mg/L |
|---|---|
| Share of wells over the level | 4.9% |
| Wells over the level / wells judged | 8 of 164 |
| Median | 0.01145 mg/L |
| Years sampled | 1935–2025 |
| Wells | 164 |
| Test results | 404 |
| Wells left out | 3 |
| Sources | USGS (239) |
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 11% |
| Wells over the level / wells judged | 16 of 150 |
| Median | 0.0075875 mg/L |
| Years sampled | 1974–2025 |
| Wells | 150 |
| Test results | 374 |
| Wells left out | 1 |
| Sources | USGS (215) |
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 30% |
| Median | 145 mg/L as CaCO₃ |
| Years sampled | 1935–2025 |
| Wells | 251 |
| Test results | 420 |
| Wells left out | 4 |
| Sources | USGS (251) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 0.3% |
| Wells over the level / wells judged | 1 of 314 |
| Median | 10 mg/L |
| Years sampled | 1935–2025 |
| Wells | 314 |
| Test results | 657 |
| Wells left out | 4 |
| Sources | USGS (314) |