Arsenic is widespread in Sacramento County wells.
1 widespread, 1 worth checking, 5 rare out of 7 health checks.
From 101 wells tested in Sacramento County since 2002; 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 37 people 43,308 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)
Less likely, but the EPA still says test your air.
Radon zones: EPA map
Here's how Sacramento County compares with California and the counties around it.
Each result puts Sacramento County next to the 8 counties that border it, on the chart's 0 to 50% scale.
This one is widespread in Sacramento County wells.
Arsenic16 of 87 wells over
Too few tested to show: Contra Costa, Solano.
This one is worth checking in Sacramento County.
Manganese7 of 87 wells over
Too few tested to show: Contra Costa, Solano.
These 5 are rare in Sacramento County.
Uranium1 of 87 wells over
Too few tested to show: Contra Costa, Solano.
Nitrate0 of 87 wells over
Too few tested to show: Contra Costa, Solano.
Radon in water0 of 11 wells over
* Likely overstated, so we don't rank it.
Too few tested to show: Amador, Contra Costa, Solano, Sutter, Yolo.
Fluoride0 of 87 wells over
Too few tested to show: Contra Costa, Solano.
Lead0 of 66 wells over
Too few tested to show: Contra Costa, Solano.
Coliform bacteria turned up in 4 of 44 tested Sacramento County wells, so test for it every year.
Coliform bacteria4 of 44 wells had it
Too few tested to show: Contra Costa, Solano, Yolo.
E. coli0 of 44 wells had it
Too few tested to show: Contra Costa, Solano, Yolo.
E. coli means human or animal waste is getting in, so if a test of your Sacramento County well finds it, boil drinking water until the well is fixed.
Iron reached staining levels in 7 of 87 tested wells, and it isn't a health risk.
Iron stains7 of 87 wells had it
Too few tested to show: Contra Costa, Solano.
Sacramento County has 101 tested wells, and the busiest decade for testing was the 2000s.
Only 14 of the 101 wells have a test from 2020 or later, so a fresh test of your own well tells you more than any of these.
Most Sacramento 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 4 things to check in Sacramento County.
- Bacteria
- Nitrate
- Arsenic
- Manganese
What California offers well owners
- Free testingThe State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. See the program
- Certified labsCalifornia's list of certified labs
- Well recordsCalifornia's well record search
Half the household wells here are shallower than 215 feet.
That comes from 7,475 household wells in California's drilling records. Most wells of every kind here are 100 to 280 feet deep. Wells as deep as Sacramento 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 31 of the 56 other California counties with enough drilling records.
Look up your own well's depth in California'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 Sacramento County.
Sacramento County is in the EPA's lowest radon zone, so radon from well water is unlikely to be a problem. Radon guide
Between 2023 and 2025 the EPA had 30 town water systems in Sacramento County test for PFAS. 10 of them had at least one test above 4 ng/L, the new EPA limit for PFOA and PFOS. The highest single result was 41 ng/L of PFOS. Only 14 wells in Sacramento County have 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 Sacramento County
Is well water in Sacramento County safe to drink?
16 of 87 wells tested in Sacramento County had arsenic over the limit, about 2 in 10. Across California it's about 1 in 7. That's a bigger share than in 39 of the 46 other California counties with 10 or more tested wells. So test your own well for arsenic before you count on it.
Can I get my well tested for free in Sacramento County?
The State and Regional Water Boards fund or regulate 11 domestic well programs that offer free well testing in their service areas. If not, use a lab California has certified for drinking water. Ask for bacteria, nitrate, arsenic and manganese, the tests that matter most in Sacramento County.
How deep are wells in Sacramento County?
Half the household wells here are shallower than 215 feet. Typical household wells here go deeper than in 31 of the 56 other California counties with enough drilling records.
How does Sacramento County compare with the counties around it?
For arsenic, the share of tested wells over the limit: 2 of the 6 neighboring counties with data had a higher share than Sacramento County, at 18%. San Joaquin had the most, at 29%. Groundwater doesn't stop at county lines, so San Joaquin's 29% is worth knowing about if you live near it.
How often should I test my well in Sacramento County?
In Sacramento County, 4 of 44 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 Sacramento County numbers come from
- People on wells: 43,308 in Sacramento County, from EPA estimates built on the 2020 Census (Murray et al.).
- Lab tests: 1,267 well water samples from 101 wells in the Water Quality Portal, run by the USGS and EPA, 2002 to 2022.
- Well depths: 7,475 California drilling records for Sacramento County, gathered in the US Groundwater Well Database (Lin and others, 2024).
- Neighboring counties: the 8 counties that share a border with Sacramento County, from the Census Bureau's county adjacency file.
- PFAS: EPA tests of 30 town water systems in Sacramento County under the Fifth Unregulated Contaminant Monitoring Rule, 2023 to 2025.
- Radon: Sacramento County is zone 3 on the EPA Map of Radon Zones.
- State programs and links: State Water Resources Control Board, checked November 1, 2026.