Arsenic and nitrate are widespread in Washoe County wells.
2 widespread, 2 worth checking, 3 rare out of 7 health checks.
From 117 wells tested in Washoe County since 2000; your own well needs its own test. How to read this
Rare: under 5%Worth checking: 5 to 15%Widespread: 15%+
Lab results: Water Quality Portal (USGS and EPA)
Who drinks from a well here
About 1 in 17 people 28,774 people
Nobody else tests these wells. Only you do.
People on wells: EPA researchers' 2020 estimate
How deep wells go here
Deep wells: fewer surface germs, more minerals from the rock.
Well depths: US Groundwater Well Database
Radon risk (a gas from rock)
Possible here. A home air test is inexpensive.
Radon zones: EPA map
Here's how Washoe County compares with Nevada and the counties around it.
Each result puts Washoe County next to the 13 counties that border it, on the chart's 0 to 50% scale.
These 2 are widespread in Washoe County wells.
Arsenic24 of 68 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Lake, OR, Pershing, Sierra, CA, Storey.
Nitrate26 of 116 wells over
Too few tested to show: Pershing, Sierra, CA, Storey.
These 2 are worth checking in Washoe County.
Manganese8 of 103 wells over
Too few tested to show: Lake, OR, Pershing, Sierra, CA, Storey.
Uranium5 of 68 wells over
Too few tested to show: Humboldt, Lake, OR, Modoc, CA, Pershing, Sierra, CA, Storey.
These 3 are rare in Washoe County.
Fluoride0 of 60 wells over
Too few tested to show: Harney, OR, Humboldt, Lake, OR, Modoc, CA, Pershing, Sierra, CA, Storey.
Lead0 of 68 wells over
Too few tested to show: Humboldt, Lake, OR, Lassen, CA, Lyon, Pershing, Sierra, CA, Storey.
Radon in water0 of 11 wells over
Too few tested to show: Carson City, Harney, OR, Humboldt, Lake, OR, Lyon, Modoc, CA, Pershing, Sierra, CA, Storey.
Coliform bacteria turned up in 1 of 26 tested Washoe County wells, so test for it every year.
Coliform bacteria1 of 26 wells had it
Too few tested to show: Churchill, Humboldt, Lake, OR, Lyon, Modoc, CA, Pershing, Sierra, CA, Storey.
E. coli0 of 26 wells had it
Too few tested to show: Churchill, Humboldt, Lake, OR, Lyon, Modoc, CA, Pershing, Sierra, CA, Storey.
E. coli means human or animal waste is getting in, so if a test of your Washoe County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 4 of 94 tested wells, and it isn't a health risk.
Iron stains4 of 94 wells had it
Too few tested to show: Lake, OR, Pershing, Sierra, CA, Storey.
Most of the 117 wells tested in Washoe County were last tested before 2010.
An old result shows the water as it was then, so treat these 117 wells as a starting point and test your own.
Most Washoe 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 5 things to check in Washoe County.
- Bacteria
- Nitrate
- Arsenic
- Manganese
- Uranium
What Nevada offers well owners
- Free testingWe didn't find a free program for all of Nevada. Nevada's private well page
- Certified labsNevada's list of certified labs
- Well recordsNevada's well record search
Half the household wells here are shallower than 195 feet.
That comes from 12,446 household wells in Nevada's drilling records. Most wells of every kind here are 119 to 300 feet deep. Wells as deep as Washoe County's are usually better protected from fertilizer and bacteria at the surface, but they can pick up more of what's in the rock, like arsenic and uranium. Typical household wells here go deeper than in 12 of the 16 other Nevada counties with enough drilling records.
Look up your own well's depth in Nevada's well record search, or see how to find it.
Well depths: US Groundwater Well Database
Here's what we know about radon and PFAS in Washoe County.
Washoe 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 4 town water systems in Washoe County test for PFAS. 1 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 20 ng/L of PFOS. No well in Washoe 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 Washoe County
Is well water in Washoe County safe to drink?
24 of 68 wells tested in Washoe County had arsenic over the limit, about 1 in 3. Across Nevada it's about 6 in 10. That's a bigger share than in 5 of the 6 other Nevada counties with 10 or more tested wells, leaving out 2 counties whose results are likely overstated. So test your own well for arsenic before you count on it.
Where can I get my well tested in Washoe County?
Use a lab Nevada has certified for drinking water. Nevada's list is linked above, in the box about testing. Ask for bacteria, nitrate, arsenic, manganese and uranium, the tests that matter most in Washoe County.
How deep are wells in Washoe County?
Half the household wells here are shallower than 195 feet. Typical household wells here go deeper than in 12 of the 16 other Nevada counties with enough drilling records.
How does Washoe County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 2 of the 9 neighboring counties with data had a higher share than Washoe County, at 35%. Churchill had the most, at 88%. Groundwater doesn't stop at county lines, so Churchill's 88% is worth knowing about if you live near it.
How often should I test my well in Washoe County?
In Washoe County, 1 of 26 tested wells had coliform bacteria, so the CDC's advice matters here: 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 Washoe County numbers come from
- People on wells: 28,774 in Washoe County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,635 well water samples from 117 wells in the Water Quality Portal, run by the USGS and EPA, 2000 to 2023.
- Well depths: 12,446 Nevada drilling records for Washoe County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 13 counties that share a border with Washoe County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 4 town water systems in Washoe County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Washoe County is zone 2 on the EPA Map of Radon Zones.
- State programs and links: Division of Environmental Protection, checked November 1, 2026.