Johnson County, Nebraska: Private Well Water Quality
USGS models estimate the private-well arsenic exposure across Johnson County, and USGS laboratory samples from at least 17 wells in the county show measured nitrate, manganese, iron and pH. The arsenic figure is an area estimate; the measurements are of other wells — neither is a test of your own well.
This is a modeled probability for the area, not a measurement of your well. USGS statistical models estimate how many private wells in this area are likely to exceed the federal limit — they cannot tell you what is in your water. Two neighbors can have very different results. The only way to know your well is to test it.
~21
people estimated to rely on private wells with modeled arsenic above the 10 µg/L EPA limit
17–25
90% confidence range for that estimate
0% of wells
sampled by USGS in the county measured outside 6.5–8.5 for pH (17 wells)
Find out what's actually in your well
Private wells are not regulated by the EPA — nobody tests wells in Johnson County for you. Arsenic, nitrate and coliform bacteria are the three most common private-well problems, and none of them has a taste or smell. A certified lab test checks all of them at once; the CDC and EPA recommend testing every well at least once a year.
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Measured well tests in Johnson County
Unlike the arsenic estimate above, these are real laboratory results: the USGS has published chemistry from at least 17 wells in Johnson County, sampled 1989–1995. They describe other wells in the county — domestic, public-supply and monitoring wells — not your well.
| Parameter | Median | Wells over threshold | What the threshold means |
|---|---|---|---|
| Nitrate (as N) | Not enough USGS well samples in Johnson County (fewer than 5) — see the state page. | ||
| Manganese | Not enough USGS well samples in Johnson County (fewer than 5) — see the state page. | ||
| Iron | Not enough USGS well samples in Johnson County (fewer than 5) — see the state page. | ||
| pH17 wells | 7.3 90th pct: 7.7 | 0%Low | outside 6.5–8.5 (EPA secondary range). Low pH is corrosive and leaches lead and copper from plumbing; high pH causes scale and bitter taste. |
What the samples show
- Nitrate (as N): Not enough USGS well samples in Johnson County — see the state page.
- Manganese: Not enough USGS well samples in Johnson County — see the state page.
- Iron: Not enough USGS well samples in Johnson County — see the state page.
- pH: pH is in the normal range for most sampled wells (median 7.3).
What to do about the biggest finding (pH): Test pH and first-draw lead and copper; a calcite or soda-ash neutralizer corrects acidic water and protects your plumbing. Read more: Lead from corroded plumbing.
Source: USGS well samples aggregated to Johnson County, Nebraska — manganese, pH and arsenic from USGS ScienceBase 5f36baa782cee144fb3873e8 (site medians, 1988–2019); nitrate and iron from McMahon et al. (2019), Environ. Sci. Technol. 53:29–38 (NWIS wells). County assignment by Census 2020 boundaries. Statistics shown only where ≥ 5 wells were sampled. USGS well samples; not a test of your well.
What the arsenic estimate means
Arsenic occurs naturally in bedrock and can dissolve into groundwater, so it shows up in private wells with no color, taste or smell. The USGS estimate above combines a statistical model of arsenic probability with the number of people on domestic wells in Johnson County. A higher number means more of your neighbors are likely drinking water over the federal limit — but your own well could be higher or lower. Long-term arsenic exposure is linked to skin, bladder and lung cancers, so the EPA sets the limit at 10 µg/L.
Statewide, Nebraska also has a modeled nitrate exceedance of 2.2% of private-well residents — worth testing for at the same time.
What to do
- Test your well for arsenic, nitrate — it's the only way to know your actual level.
- If arsenic or nitrate is present, install a reverse-osmosis system — carbon pitchers do not remove either.
- Re-test annually; well chemistry changes over time.
Match the filter to your test result
Carbon pitchers and faucet filters do not remove arsenic or nitrate. Reverse osmosis is the point-of-use fix; a whole-house system handles the rest of the home.
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Under-sink RO removes arsenic, nitrate, lead and PFAS at the kitchen tap.
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Treats every tap, shower and appliance — the right scale for sediment, iron, sulfur and bacteria on a private well.
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5-stage RO, ★ 4.7 — removes arsenic, nitrate, lead, fluoride and PFAS.
Check price on Amazon →Affiliate links — we may earn a commission at no extra cost to you. Re-test after installing to confirm the system is working.