Well water in Adams County, Idaho
In Adams County, none of 74 tested well samples exceeded the EPA limit for nitrate, based on public data from Idaho statewide ground water quality monitoring (IDWR EDMS) and USGS Water Quality Portal.
76 individual samples from 14 wells, 1990 to 2024. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Adams County. Above limit means above the EPA maximum contaminant level; where EPA has no enforceable limit, the row shows a health guideline or nuisance level instead.
| Contaminant | Samples | Detected | Above limit | Median | Highest | Limit | |
|---|---|---|---|---|---|---|---|
| Nitrate 1990 to 2024 | 74 | 78% | 0% | 0.402 | 4.7 | 10 mg/L EPA limit | |
| Fluoride 1990 to 2024 | 70 | 73% | 0% | 0.17 | 0.57 | 4 mg/L EPA limit | |
| Arsenic 1990 to 2024 | 69 | 59% | 0% | 0.52 | 5.5 | 10 ug/L EPA limit | |
| Nitrite 1991 to 2011 | 52 | 10% | 0% | 0 | 0.02 | 1 mg/L EPA limit | |
| E. coli 1990 to 2008 | 46 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Copper 1990 to 2019 | 46 | 13% | 0% | 0 | 0.004 | 1.3 mg/L EPA limit | |
| Lead 1990 to 2002 | 26 | 4% | 0% | 0 | 1 | 15 ug/L EPA limit | |
| Uranium 2016 to 2024 | 11 | 0% | 0% | 0 | 0 | 30 ug/L EPA limit | |
| Chloride 1990 to 2024 | 76 | 97% | no limit | 1.67 | 78.8 | 250 mg/L nuisance level | |
| Sodium 1990 to 2024 | 74 | 100% | no limit | 9.74 | 27.8 | 20 mg/L health guideline | |
| Iron 1990 to 2024 | 71 | 44% | no limit | 0 | 2,180 | 300 ug/L nuisance level | |
| Manganese 1990 to 2024 | 70 | 44% | no limit | 0 | 513 | 300 ug/L health guideline |
Sampled fewer than 10 times, too few to summarize: Radon (7).
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What this means
Among contaminants with a federal limit, no tested sample in Adams County came back above it. That is reassuring, but sampling is uneven: wells that were never tested are not in this data.
Chloride is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Adams County
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 680 pCi/L.
- NitrateRecommended for every private well, especially near farms or septic systems.
- ChlorideDetected in 97% of local samples.
- FluorideDetected in 73% of local samples.
Treatment that fits the local profile
- Fluoride
- Point-of-use reverse osmosis; Activated alumina; Distillation
- Chloride
- Point-of-use reverse osmosis; Distillation
Get your Adams County water tested at home
A licensed local water treatment company tests your tap water in your home, walks you through the numbers, and quotes treatment only if something needs fixing. Free, about 30 minutes, no obligation. Tell us what you need and we match you with a company that serves Adams County.
Common questions
Is there arsenic in well water in Adams County?
Arsenic was detected in 59% of 69 public well samples in Adams County, and 0% were above the EPA limit of 10 ug/L. Arsenic has no taste or smell; a lab test is the only way to know your level.
How high is radon in well water in Adams County?
The median radon level across 7 public samples in Adams County was 680 pCi/L, with a high of 1,500 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Adams County?
Test for bacteria and nitrate every year. Test once for arsenic, uranium, radon, fluoride, manganese and PFAS, then again every three to five years or after any change in taste, color, or plumbing.
Sources
- Idaho statewide ground water quality monitoring (IDWR EDMS): 680 samples in Adams County. Ground water quality results from the Idaho Department of Water Resources statewide monitoring program and partner agencies (ISDA, IDEQ, INL), EDMS bulk download. Retrieved September 9, 2026.
- USGS Water Quality Portal: 12 samples in Adams County. Data from the Water Quality Portal, a service of USGS, EPA and USDA; groundwater samples collected by USGS and cooperators. Retrieved September 3, 2026.
Non-detects count as samples and are treated as zero when computing medians. Exactly at the limit counts as not above it. A sample belongs to the town containing the well's reported coordinates.