Well water in San Bernardino County, California
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Testing strongly recommended
tested well samples in San Bernardino County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.
44,813 test results across 15 contaminants from at least 2,094 wells, 1908 to 2026; sodium has the most at 8,464. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 747 people in San Bernardino County get their drinking water from a private well, per USGS 2015 county water use. That is about <1% of residents.
Separately, the USGS national arsenic model estimates that 100% of the 747 people on private wells in San Bernardino County draw water above 10 ug/L, from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside San Bernardino 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 | Above limit | Samples | Detected | Median | Highest | Limit |
|---|---|---|---|---|---|---|
| Arsenic 1951 to 2026 | 4,608 | 90% | 2.5 | 970 | 10 ug/L EPA limit | |
| Uranium 1993 to 2026 | 1,240 | 98% | 4.58 | 1,470 | 30 ug/L EPA limit | |
| Fluoride 1932 to 2026 | 8,460 | 99% | 0.6 | 170 | 4 mg/L EPA limit | |
| Nitrate 1943 to 2026 | 6,244 | 92% | 1.5 | 122 | 10 mg/L EPA limit | |
| PFOA 2020 to 2023 | 45 | 20% | 0 | 4.3 | 4 ng/L EPA limit | |
| PFOS 2020 to 2023 | 45 | 16% | 0 | 12 | 4 ng/L EPA limit | |
| Radium (226 + 228) 1997 to 2022 | 253 | 69% | 0.04 | 14.2 | 5 pCi/L EPA limit | |
| Lead 1959 to 2024 | 1,531 | 28% | 0 | 900 | 15 ug/L EPA limit | |
| Copper 1951 to 2024 | 1,170 | 36% | 0 | 0.39 | 1.3 mg/L EPA limit | |
| E. coli 2006 to 2022 | 56 | 0% | 0 | 0 | 0 MPN/100mL EPA limit | |
| Sodium 1908 to 2026 | no limit | 8,464 | 100% | 72.5 | 90,000 | 20 mg/L health guideline |
| Iron 1916 to 2026 | no limit | 7,044 | 56% | 4 | 460,000 | 300 ug/L nuisance level |
| Manganese 1932 to 2026 | no limit | 5,521 | 58% | 0.35 | 10,500 | 300 ug/L health guideline |
| Radon 2000 to 2016 | no limit | 121 | 100% | 520 | 19,300 | 2,000 pCi/L health guideline |
| Chloride 1953 to 1987 | no limit | 11 | 100% | 1,100 | 32,000 | 250 mg/L nuisance level |
Over time
Share of samples above the limit by period. A cell needs ten samples to show; a comparison needs twenty in each period. Later periods sample fewer wells, and often the ones already known to have a problem.
| Contaminant | before 2000 | 2000s | 2010s | 2020s |
|---|---|---|---|---|
| Fluoride | 8%5,251 samples | 5%1,292 samples | 9%1,684 samples | 9%233 samples |
| Nitrate | 6%3,255 samples | 5%1,280 samples | 7%1,489 samples | 7%220 samples |
| Arsenic | 26%1,364 samples | 14%1,341 samples | 26%1,692 samples | 27%211 samples |
| Lead | 6%86 samples | 0%362 samples | 0%968 samples | 0%115 samples |
| Uranium | 12%41 samples | 2%253 samples | 11%779 samples | 7%167 samples |
| Copper | 0%144 samples | 0%362 samples | 0%564 samples | 0%100 samples |
Fluoride, nitrate, arsenic, lead, uranium, copper have held within a few points between the two most recent periods with enough samples.
Closer than the county
See the sampled wells near your address
The same records, drawn around one point: which wells within a few miles were sampled and what they found, how deep the wells next to you were drilled, and any leaking tank or cleanup site within a mile.
Check my addressWhat this means
The contaminants most often above their limit here are arsenic (23% of 4,608 samples), uranium (8% of 1,240 samples), and fluoride (8% of 8,460 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.
Iron, Manganese, and Chloride 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 San Bernardino County
- 1Arsenic23% of 4,608 local samples were above the limit.
- 2Uranium8% of 1,240 local samples were above the limit.
- 3Fluoride8% of 8,460 local samples were above the limit.
- 4Nitrate6% of 6,244 local samples were above the limit.
- 5PFOA4% of 45 local samples were above the limit.
- 6PFOS2% of 45 local samples were above the limit.
- 7Radium (226 + 228)<1% of 253 local samples were above the limit.
- 8Volatile organic compounds (VOCs)1,348 leaking underground storage tank sites on record locally.
- 9Metals panel46 hazardous waste sites on record locally.
Test your San Bernardino County well for arsenic, uranium and fluoride
Certified lab analysis of your own tap water, bottles and prepaid return shipping included. The Essential well panel covers arsenic, uranium, nitrate, lead, copper, manganese, iron, sodium and bacteria; radon and PFAS are add-ons.
Order the Tap Score well water test kit, from $209Already tested? Upload the report
Just want bacteria checked first? Tap Score coliform and E. coli test, $99. Coliform and E. coli are the tests every well needs every year.
Want a quick look before paying for a lab? Home well water test strips on Amazon check hardness, iron, pH and nitrate in minutes. They are a screen, not a result: arsenic, bacteria, uranium and PFAS need a certified lab.
Affiliate links: the merchant pays us a commission and the price is the same for you. It does not change what the data above says. As an Amazon Associate we earn from qualifying purchases.
Where to get a well tested in California: certified labs, state programs and prices.
Already have results back? Get your lab report read against the San Bernardino County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
The rock under San Bernardino County
Basin and Range basin-fill aquifers
Unconsolidated sand and gravel. Wells in sand and gravel are usually shallow and productive, and they recharge quickly from the surface. That makes them the most exposed to nitrate, bacteria and anything spilled nearby, and the least likely to carry arsenic or radon from the rock.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the county centroid. A single well can sit in a different unit, especially near a boundary.
Official help in California
Two places to start that are not selling anything: the state program that answers private well questions, and its list of labs certified to run drinking water tests. A certified lab is the difference between a result you can act on and a number.
- GAMA - Well Owners, State Water Resources Control Board
- Environmental Laboratory Accreditation Program (ELAP), State Water Resources Control Board
Contamination sources on record in San Bernardino County
California GeoTracker and EnviroStor sites records 1,348 leaking underground storage tank sites and 46 hazardous waste sites in San Bernardino County, among 2,643 regulated sites in total. Groundwater does not follow property lines, so a well within a few hundred feet of one of these is worth testing for what that site could release.
- 1,348
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 46
- hazardous waste sitesSolvents, degreasers and metals from industrial sites can travel far in fractured bedrock.
- 163
- lined landfills and transfer facilities
- 1,086
- other remediation projects
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Systems we would look at first
Some links below are affiliate links. If you buy through one, the merchant pays us a commission at no extra cost to you. It does not change which products we list or what the data says.
For arsenic
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
For arsenic
Whole-house arsenic and uranium filter
whole-house, at the point of entry, about $2,500
Adsorptive iron-based media; sized to your well yield.
For arsenic
Aquasana SmartFlow reverse osmosis
under-sink or countertop, about $225
Certified to NSF/ANSI 58 and 53 to reduce arsenic (96%, pentavalent), fluoride (90%), lead (99%), nitrate, nitrite and PFOA/PFOS at the kitchen tap, with a remineralizer.
For PFOA
Aquasana Claryum 3-Stage under-sink filter
under-sink or countertop, about $175
Certified to NSF/ANSI 53 to reduce 99% of lead and 99.7% of PFOA and PFOS at the tap. Not a fix for arsenic, nitrate or bacteria.
For PFOA
Whole-house PFAS carbon system
whole-house, at the point of entry, about $3,000
Granular activated carbon certified to NSF/ANSI 53 for PFOA and PFOS; replace media on schedule.
For PFOA
Aquasana HealthShield whole-house filter
whole-house, at the point of entry, about $2,099
Whole-house carbon system the maker certifies to reduce PFAS (PFOA and PFOS) and VOCs at every tap; a UV option adds bacteria protection.
Free, no obligation
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No water treatment company serves San Bernardino County through Well Water Nerd yet. We are signing licensed companies on county by county: they test at your tap for free, walk you through the numbers, and quote treatment only if something needs fixing. Leave your details and you are first in line. Nothing is shared until a company joins for San Bernardino County, and you get an email naming it first.
Common questions
Is there arsenic in well water in San Bernardino County?
Arsenic was detected in 90% of 4,608 public well samples in San Bernardino County, and 23% 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 San Bernardino County?
The median radon level across 121 public samples in San Bernardino County was 520 pCi/L, with a high of 19,300 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in San Bernardino 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.
Counties near San Bernardino County
Closest first. Groundwater does not stop at a line on a map, so the next county over is a fair second opinion.
Want the numbers themselves? Download the California dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 44,813 samples in San Bernardino 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.
- USGS national arsenic model (Ayotte 2017): estimated share of 747 people on private wells in San Bernardino County above 10 ug/L of arsenic, from geology, well depth and land use. County estimates of domestic well users with arsenic above 10 ug/L from the USGS national logistic regression model (Ayotte, Medalie and Qi, 2017), with private well population from the USGS 2015 county water-use compilation (Dieter and others, 2018). Retrieved September 15, 2026.
- California GeoTracker and EnviroStor sites: 2,643 regulated sites located in San Bernardino County. Leaking underground storage tank and cleanup sites from the State Water Board GeoTracker export on data.ca.gov, and DTSC EnviroStor cleanup sites. Retrieved September 15, 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.