Well water in Valley County, Idaho
In Valley County, none of 132 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.
135 individual samples from 33 wells, 1982 to 2025. Data refreshed September 9, 2026.
What individual samples found
Each row summarizes every public sample for that contaminant inside Valley 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 | |
|---|---|---|---|---|---|---|---|
| Total coliform 2022 | 12 | 8% | 8% | 0 | 5 | 0 MPN/100mL EPA limit | |
| Nitrate 1982 to 2025 | 132 | 64% | 0% | 0.14 | 8.6 | 10 mg/L EPA limit | |
| Fluoride 1982 to 2025 | 117 | 48% | 0% | 0 | 1.67 | 4 mg/L EPA limit | |
| Arsenic 1990 to 2025 | 112 | 36% | 0% | 0 | 4.7 | 10 ug/L EPA limit | |
| Nitrite 1991 to 2022 | 93 | 11% | 0% | 0 | 0.02 | 1 mg/L EPA limit | |
| Copper 1990 to 2019 | 80 | 34% | 0% | 0 | 0.046 | 1.3 mg/L EPA limit | |
| E. coli 1990 to 2008 | 75 | 0% | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Lead 1990 to 2002 | 43 | 2% | 0% | 0 | 0.15 | 15 ug/L EPA limit | |
| Uranium 2016 to 2025 | 21 | 0% | 0% | 0 | 0 | 30 ug/L EPA limit | |
| Sodium 1990 to 2025 | 135 | 100% | no limit | 5.7 | 38 | 20 mg/L health guideline | |
| Chloride 1990 to 2025 | 133 | 98% | no limit | 0.9 | 58.3 | 250 mg/L nuisance level | |
| Iron 1990 to 2025 | 122 | 82% | no limit | 118 | 10,500 | 300 ug/L nuisance level | |
| Manganese 1990 to 2025 | 120 | 82% | no limit | 39 | 1,000 | 300 ug/L health guideline | |
| Radon 1991 to 1994 | 20 | 100% | no limit | 340 | 510 | 2,000 pCi/L health guideline |
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What this means
The contaminants most often above their limit here are total coliform (8% of 12 samples). A well next door can differ sharply from yours because bedrock fractures, well depth and plumbing all matter, so these rates describe the area, not your tap.
Chloride, Iron, and Manganese are widespread in local groundwater. They are mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Valley County
- Total coliform8% of 12 local samples were above the limit.
- Coliform bacteriaRecommended for every private well, every year.
- RadonMedian local reading is 340 pCi/L.
- NitrateRecommended for every private well, especially near farms or septic systems.
- ChlorideDetected in 98% of local samples.
- IronDetected in 82% of local samples.
- ManganeseDetected in 82% of local samples.
Treatment that fits the local profile
- Total coliform
- Inspect and repair the well cap and casing, then shock chlorinate and retest; UV disinfection whole-house; Chlorination system
- Chloride
- Point-of-use reverse osmosis; Distillation
- Iron
- Oxidizing filter whole-house; Water softener (low levels); Aeration plus filtration
- Manganese
- Oxidizing filter (greensand, birm) whole-house; Water softener (low levels); Point-of-use reverse osmosis
Get your Valley 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 Valley County.
Common questions
Is there arsenic in well water in Valley County?
Arsenic was detected in 36% of 112 public well samples in Valley 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 Valley County?
The median radon level across 20 public samples in Valley County was 340 pCi/L, with a high of 510 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Valley 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): 1,188 samples in Valley 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: 27 samples in Valley 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.