Well water in Arizona
1in3
Testing strongly recommended
tested well samples in Arizona exceeded the EPA limit for PFOA (4 ng/L), based on public data from USGS Water Quality Portal.
128,513 test results across 15 contaminants from at least 10,876 wells, 1917 to 2026; chloride has the most at 24,358. Data refreshed September 15, 2026.
Compiled by Nick at Well Water Nerd from public records. How these pages are built
An estimated 218,170 people in Arizona get their drinking water from a private well, per USGS 2015 county water use.
Separately, the USGS national arsenic model estimates that 8% of the 218,170 people on private wells in Arizona draw water above 10 ug/L (the model's range is 6% to 10%), from geology and well depth rather than local tests.
What individual samples found
Each row summarizes every public sample for that contaminant inside Arizona. 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 |
|---|---|---|---|---|---|---|
| PFOA 2021 to 2026 | 533 | 67% | 2.1 | 140 | 4 ng/L EPA limit | |
| Nitrate 1917 to 2026 | 20,963 | 94% | 3.16 | 1,700 | 10 mg/L EPA limit | |
| Arsenic 1963 to 2026 | 6,628 | 66% | 3 | 2,300 | 10 ug/L EPA limit | |
| Fluoride 1933 to 2026 | 18,248 | 98% | 0.7 | 1,280 | 4 mg/L EPA limit | |
| Uranium 1957 to 2026 | 723 | 95% | 4 | 122 | 30 ug/L EPA limit | |
| Copper 1933 to 2026 | 6,478 | 38% | 0 | 224 | 1.3 mg/L EPA limit | |
| Lead 1968 to 2026 | 6,119 | 20% | 0 | 700 | 15 ug/L EPA limit | |
| Radium (226 + 228) 1958 to 2026 | 899 | 41% | 0 | 113 | 5 pCi/L EPA limit | |
| E. coli 1998 to 2023 | 143 | 1% | 0 | 120 | 0 MPN/100mL EPA limit | |
| Chloride 1917 to 2026 | no limit | 24,358 | 100% | 137 | 190,000 | 250 mg/L nuisance level |
| Sodium 1917 to 2026 | no limit | 19,491 | 100% | 138 | 40,200 | 20 mg/L health guideline |
| Iron 1917 to 2026 | no limit | 12,244 | 56% | 3 | 3,200,000 | 300 ug/L nuisance level |
| Manganese 1955 to 2026 | no limit | 10,800 | 46% | 0 | 672,000 | 300 ug/L health guideline |
| Radon 1989 to 2018 | no limit | 885 | 100% | 440 | 250,000 | 2,000 pCi/L health guideline |
Sampled fewer than 10 times, too few to summarize: PFOS (1).
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 |
|---|---|---|---|---|
| Nitrate | 28%17,591 samples | 19%1,710 samples | 10%624 samples | 17%1,038 samples |
| Fluoride | 11%15,033 samples | 9%2,289 samples | 15%660 samples | 9%266 samples |
| Arsenic | 28%3,793 samples | 19%1,823 samples | 34%666 samples | 19%346 samples |
| Copper | 7%3,827 samples | 2%1,824 samples | <1%584 samples | <1%243 samples |
| Lead | 4%3,515 samples | <1%1,732 samples | <1%619 samples | 2%253 samples |
| Radium (226 + 228) | 7%154 samples | 2%390 samples | 0%169 samples | 0%186 samples |
Nitrate above the limit in Arizona rose from 10% of 624 samples in the 2010s to 17% of 1038 in the 2020s.
Fluoride above the limit in Arizona fell from 15% of 660 samples in the 2010s to 9% of 266 in the 2020s.
Arsenic above the limit in Arizona fell from 34% of 666 samples in the 2010s to 19% of 346 in the 2020s.
Copper, lead, radium (226 + 228) have held within a few points between the two most recent periods with enough samples.
What this means
The contaminants most often above their limit here are pfoa (40% of 533 samples), nitrate (26% of 20,963 samples), and arsenic (26% of 6,628 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 and Iron 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 Arizona
- 1PFOA40% of 533 local samples were above the limit.
- 2Nitrate26% of 20,963 local samples were above the limit.
- 3Arsenic26% of 6,628 local samples were above the limit.
- 4Fluoride11% of 18,248 local samples were above the limit.
- 5Uranium7% of 723 local samples were above the limit.
- 6Copper5% of 6,478 local samples were above the limit.
- 7Lead2% of 6,119 local samples were above the limit.
- 8Volatile organic compounds (VOCs)4,842 leaking underground storage tank sites on record locally.
Test your Arizona well for PFOA, nitrate and arsenic
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 Arizona numbers, $29. Every line explained, ranked by what matters, with the fix for each.
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Send me the Arizona report
The numbers above, which tests to order and where, and the treatment that fits the local profile, in one email.
Wells in Arizona
140,485 domestic wells in Arizona are on record with the state since 1970. the typical well is 300 feet deep (one in ten goes past 638 feet).
In a typical Arizona well, the median yield is 15 gallons per minute, 4% 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 Arizona
Not a principal aquifer
The USGS map places this area outside any principal aquifer, which usually means wells here draw from fractured bedrock or thin local deposits rather than a large regional aquifer. Bedrock wells of that kind are where arsenic, radon and uranium turn up, and yields vary from well to well.
Classification from the USGS Principal Aquifers of the United States (national map, 2003 edition, GIS release 2015), read at the state 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 Arizona
ADEQ records 4,842 leaking underground storage tank sites in Arizona, among 4,885 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.
- 4,842
- leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
- 43
- lined landfills and transfer facilities
Treatment that fits the local profile
PFOA
Granular activated carbon whole-house; Point-of-use reverse osmosis; Anion exchange
Nitrate
Point-of-use reverse osmosis; Anion exchange; Distillation
Arsenic
Point-of-use reverse osmosis; Adsorptive media (iron-based) whole-house; Anion exchange
Fluoride
Point-of-use reverse osmosis; Activated alumina; Distillation
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 PFOA
Under-sink reverse osmosis system
under-sink or countertop, about $300
Look for NSF/ANSI 58 certification listing the contaminant you need removed.
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 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 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 copper
Acid neutralizing filter
whole-house, at the point of entry, about $1,200
Raises pH so plumbing stops leaching lead and copper.
Common questions
How deep are wells in Arizona?
The typical domestic well in Arizona is 300 feet deep, based on 140,485 wells reported to the state since 1970. One in ten is deeper than 638 feet.
Is there arsenic in well water in Arizona?
Arsenic was detected in 66% of 6,628 public well samples in Arizona, and 26% 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 Arizona?
The median radon level across 885 public samples in Arizona was 440 pCi/L, with a high of 250,000 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.
How often should I test a private well in Arizona?
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 in Arizona
Want the numbers themselves? Download the Arizona dataset as CSV, every county and town, with the sources named.
Sources
- USGS Water Quality Portal: 128,513 samples in Arizona. 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 218,170 people on private wells in Arizona 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): 240,994 well records in Arizona, 140,485 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: 4,885 regulated sites located in Arizona. 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.