Well water in Cochise County, Arizona
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Testing recommended
tested well samples in Cochise County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.
8,740 test results across 13 contaminants from at least 1,177 wells, 1920 to 2024; chloride has the most at 1,752. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 23,800 people in Cochise County get their drinking water from a private well, per USGS 2015 county water use. That is about 19% of residents.
Separately, the USGS national arsenic model estimates that 5% of the 23,800 people on private wells in Cochise County draw water above 10 ug/L (the model's range is 4% to 7%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Cochise 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 1980 to 2024 | 527 | 42% | 0 | 150 | 10 ug/L EPA limit | |
| Fluoride 1934 to 2024 | 1,546 | 99% | 0.93 | 282 | 4 mg/L EPA limit | |
| Nitrate 1920 to 2024 | 1,024 | 98% | 1.2 | 62 | 10 mg/L EPA limit | |
| Radium (226 + 228) 1995 to 2013 | 56 | 23% | 0 | 18 | 5 pCi/L EPA limit | |
| Uranium 1957 to 2024 | 42 | 93% | 4.39 | 42.1 | 30 ug/L EPA limit | |
| Copper 1964 to 2024 | 520 | 36% | 0 | 0.058 | 1.3 mg/L EPA limit | |
| Lead 1979 to 2024 | 519 | 14% | 0 | 11 | 15 ug/L EPA limit | |
| Chloride 1920 to 2024 | no limit | 1,752 | 100% | 12 | 40,500 | 250 mg/L nuisance level |
| Sodium 1940 to 2024 | no limit | 944 | 100% | 35 | 39,700 | 20 mg/L health guideline |
| Manganese 1956 to 2021 | no limit | 877 | 33% | 0 | 1,520 | 300 ug/L health guideline |
| Iron 1920 to 2021 | no limit | 867 | 45% | 0 | 13,900 | 300 ug/L nuisance level |
| Radon 1996 to 2013 | no limit | 62 | 100% | 585 | 4,419 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: E. coli (4).
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 | 10%1,324 samples | 8%212 samples | n/a | n/a |
| Nitrate | 8%865 samples | 11%140 samples | 0%10 samples | n/a |
| Arsenic | 13%399 samples | 11%118 samples | n/a | n/a |
| Copper | 0%393 samples | 0%118 samples | n/a | n/a |
| Lead | 0%391 samples | 0%118 samples | n/a | n/a |
Fluoride, nitrate, arsenic, copper, lead 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 (12% of 527 samples), fluoride (9% of 1,546 samples), and nitrate (8% of 1,024 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 is widespread in local groundwater. It is mainly a staining and taste problem, but high manganese also carries a health advisory for infants.
What to test for in Cochise County
- 1Arsenic12% of 527 local samples were above the limit.
- 2Fluoride9% of 1,546 local samples were above the limit.
- 3Nitrate8% of 1,024 local samples were above the limit.
- 4Radium (226 + 228)7% of 56 local samples were above the limit.
- 5Uranium5% of 42 local samples were above the limit.
- 6Coliform bacteriaRecommended for every private well, every year.
- 7RadonMedian local reading is 585 pCi/L.
- 8Volatile organic compounds (VOCs)188 leaking underground storage tank sites on record locally.
Test your Cochise County well for arsenic, fluoride and nitrate
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 Arizona: certified labs, state programs and prices.
Already have results back? Get your lab report read against the Cochise County numbers, $29. Every line explained, ranked by what matters, with the fix for each.
Wells in Cochise County
15,085 domestic wells in Cochise County are on record with the state since 1970. the typical well is 272 feet deep (one in ten goes past 600 feet).
In a typical Cochise County well, the median yield is 16 gallons per minute, 2% of wells yield under 3 gallons per minute and usually need a storage tank.
Find your own well's report
The state keeps the driller's report for most wells drilled since 1984. It tells you how deep your well is, where bedrock starts, and how much water it makes, which decides what treatment can work.
- Open ADWR Wells55 registry and choose Water Well.
- The record lists depth, water level, casing depth and the tested rate, plus a link to the drilling log.
Arizona has registered wells since 1980; earlier wells often have no record.
The rock under Cochise 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 Arizona
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.
Contamination sources on record in Cochise County
ADEQ records 188 leaking underground storage tank sites in Cochise County, among 191 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.
- 188
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 3
- lined landfills and transfer facilities
Treatment that fits the local profile
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Radium (226 + 228)
Water softener (cation exchange); Point-of-use reverse osmosis
Uranium
Point-of-use reverse osmosis; Anion exchange; Whole-house 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.
Free, no obligation
Get on the list for a free in-home water test in Cochise County
No water treatment company serves Cochise 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 Cochise County, and you get an email naming it first.
Common questions
How deep are wells in Cochise County?
The typical domestic well in Cochise County is 272 feet deep, based on 15,085 wells reported to the state since 1970. One in ten is deeper than 600 feet.
Is there arsenic in well water in Cochise County?
Arsenic was detected in 42% of 527 public well samples in Cochise County, and 12% 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 Cochise County?
The median radon level across 62 public samples in Cochise County was 585 pCi/L, with a high of 4,419 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Cochise 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 Cochise 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 Arizona dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 8,740 samples in Cochise 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 23,800 people on private wells in Cochise 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.
- Arizona ADWR well registry (Wells55): 24,263 well records in Cochise County, 15,085 domestic. Registered wells from the Arizona Department of Water Resources Wells55 registry. Only aggregates are shown; owner names and addresses are never stored. Retrieved September 18, 2026.
- ADEQ regulated sites: 191 regulated sites located in Cochise County. Leaking underground storage tank sites and municipal landfills from the Arizona Department of Environmental Quality. Retrieved September 18, 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.