Otter Tail County, MN
These figures come from wells tested in Otter Tail County, MN, not from any one well.
- Iron is common in wells in Otter Tail County, MN (165 of 200 tested wells were over that level), so it's worth testing for.
- Manganese is common in wells in Otter Tail County, MN (155 of 188 tested wells were over that level), so it's worth testing for.
- Sulfate is not common in wells in Otter Tail County, MN (12 of 390 tested wells were over). Only a test tells you about your own well.
- Wells in Otter Tail County, MN are typically very hard (370 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:
- iron (common in wells here)
- manganese (common in wells here)
- 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. Minnesota'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 | 82% |
| Wells over the level / wells judged | 165 of 200 |
| Median | 1.695 mg/L |
| Years sampled | 1964–2025 |
| Wells | 200 |
| Test results | 665 |
| Wells left out | 15 |
| Sources | MNDNR_AGW (215), USGS (123), MNPCA_AGW (46) |
Manganese Recent
| Level it's compared with | 0.05 mg/L |
|---|---|
| Share of wells over the level | 82% |
| Wells over the level / wells judged | 155 of 188 |
| Median | 0.16025 mg/L |
| Years sampled | 1964–2025 |
| Wells | 188 |
| Test results | 526 |
| Wells left out | 15 |
| Sources | MNDNR_AGW (215), USGS (123), MNPCA_AGW (35) |
Hardness Recent
| Level it's compared with | none; hardness is shown in bands |
|---|---|
| Share of wells very hard | 97% |
| Median | 316.694 mg/L as CaCO₃ |
| Years sampled | 1964–2025 |
| Wells | 370 |
| Test results | 521 |
| Wells left out | 15 |
| Sources | MNDNR_AGW (215), USGS (123), MNPCA_AGW (32) |
Sulfate Recent
| Level it's compared with | 250 mg/L |
|---|---|
| Share of wells over the level | 3.1% |
| Wells over the level / wells judged | 12 of 390 |
| Median | 13 mg/L |
| Years sampled | 1964–2025 |
| Wells | 390 |
| Test results | 564 |
| Wells left out | 15 |
| Sources | MNDNR_AGW (215), USGS (122), MNPCA_AGW (53) |