Arsenic is widespread in Canyon County wells.
1 widespread, 1 worth checking, 3 rare out of 5 health checks.
From 171 wells tested in Canyon County since 2000; your own well needs its own test. How to read this
Not charted, because fewer than 10 wells were tested: uranium (1).
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
1 in 5 people 48,746 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Canyon County compares with Idaho and the counties around it.
Each result puts Canyon County next to the 5 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Canyon County wells.
Arsenic65 of 163 wells over
* Likely overstated, so we don't rank it.
This one is worth checking in Canyon County.
Nitrate18 of 169 wells over
* Likely overstated, so we don't rank it.
These 3 are rare in Canyon County.
Manganese8 of 161 wells over
Fluoride1 of 161 wells over
Too few tested to show: Malheur, OR.
Lead0 of 39 wells over
Too few tested to show: Payette.
Too few Canyon County wells were tested for this one.
Uranium1 well tested
Every well needs a bacteria test every year.
No bacteria tests from Canyon County wells are in the public data. Test every year anyway.
Iron reached staining levels in 13 of 161 tested wells, and it isn't a health risk.
Iron stains13 of 161 wells had it
Most of the 171 wells tested in Canyon County were last tested before 2010.
An old result shows the water as it was then, so treat these 171 wells as a starting point and test your own.
Most Canyon County wells in these records were tested for research or because someone suspected a problem, which can push the shares above what a typical home well would show (how we read the numbers).
One mail-in lab test covers the 3 things to check in Canyon County.
- Bacteria
- Nitrate
- Arsenic
What Idaho offers well owners
- Free testingDHW offers free private well water testing kits through Idaho Health Tools, limited to one kit per household every five years. See the program
- Certified labsIdaho's list of certified labs
- Well recordsIdaho's well record search
Here's what we know about radon and PFAS in Canyon County.
Canyon County is in the EPA's middle radon zone. An indoor air test is cheap and tells you whether to look at your water. Radon guide
Between 2023 and 2025 the EPA had 3 town water systems in Canyon County test for PFAS. None found any. No well in Canyon County has public PFAS results, so the town systems are the best clue to what's in the groundwater nearby. PFAS guide
Radon zones: EPA Map of Radon Zones. PFAS: EPA tests of town water systems, 2023 to 2025
Questions people ask about well water in Canyon County
Is well water in Canyon County safe to drink?
65 of 163 wells tested in Canyon County had arsenic over the limit, about 4 in 10. Across Idaho it's about 1 in 10. That's a bigger share than in 38 of the 42 other Idaho counties with 10 or more tested wells, leaving out 1 county whose results are likely overstated. So test your own well for arsenic before you count on it.
Can I get my well tested for free in Canyon County?
DHW offers free private well water testing kits through Idaho Health Tools, limited to one kit per household every five years. If not, use a lab Idaho has certified for drinking water. Ask for bacteria, nitrate and arsenic, the tests that matter most in Canyon County.
How does Canyon County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 3 of the 5 neighboring counties with data had a higher share than Canyon County, at 40%. Malheur, OR had the most, at 94%. Groundwater doesn't stop at county lines, so Malheur, OR's 94% is worth knowing about if you live near it.
How often should I test my well in Canyon County?
Canyon County has no public bacteria results for wells, so follow the CDC's advice: test for bacteria and nitrate every year, and right away after a flood, a repair, or any change in taste or smell.
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Where the Canyon County numbers come from
- People on wells: 48,746 in Canyon County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 2,318 well water samples from 171 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2013.
- Neighboring counties: the 5 counties that share a border with Canyon County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 3 town water systems in Canyon County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Canyon County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Department of Health and Welfare, checked November 1, 2026.