Well water in Pinal County, Arizona

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Testing strongly recommended

tested well samples in Pinal County exceeded the EPA limit for arsenic (10 ug/L), based on public data from USGS Water Quality Portal.

8,325 test results across 13 contaminants from at least 1,130 wells, 1941 to 2026; chloride has the most at 1,780. Data refreshed September 15, 2026.

Compiled by Nick at Well Water Nerd from public records. How these pages are built

An estimated 12,570 people in Pinal County get their drinking water from a private well, per USGS 2015 county water use. That is about 3% of residents.

Separately, the USGS national arsenic model estimates that 4% of the 12,570 people on private wells in Pinal County draw water above 10 ug/L (the model's range is 3% to 5%), from geology and well depth rather than local tests.

What individual samples found

Each row summarizes every public sample for that contaminant inside Pinal 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 1977 to 2026	36%	417	71%	4	264	10 ug/L EPA limit
Nitrate 1941 to 2026	29%	1,246	99%	5	220	10 mg/L EPA limit
Fluoride 1941 to 2026	8%	1,469	99%	0.8	220	4 mg/L EPA limit
Lead 1978 to 2026	<1%	395	13%	0	100	15 ug/L EPA limit
Copper 1977 to 2026	0%	407	29%	0	0.08	1.3 mg/L EPA limit
Radium (226 + 228) 1958 to 2022	0%	43	23%	0	2.96	5 pCi/L EPA limit
Uranium 1958 to 2013	0%	13	92%	4.3	28	30 ug/L EPA limit
Chloride 1941 to 2026	no limit	1,780	100%	75	10,400	250 mg/L nuisance level
Iron 1950 to 2026	no limit	857	59%	0	7,200	300 ug/L nuisance level
Sodium 1941 to 2026	no limit	839	100%	110	1,180	20 mg/L health guideline
Manganese 1957 to 2026	no limit	801	37%	0	780	300 ug/L health guideline
Radon 1998 to 2013	no limit	56	100%	363	6,757	2,000 pCi/L health guideline

Sampled fewer than 10 times, too few to summarize: E. coli (2).

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%1,272 samples	8%186 samples	n/a	n/a
Nitrate	26%1,130 samples	55%106 samples	n/a	n/a
Arsenic	43%249 samples	27%157 samples	n/a	n/a
Copper	0%242 samples	0%156 samples	n/a	n/a
Lead	1%230 samples	0%156 samples	n/a	n/a

Nitrate above the limit in Pinal County rose from 26% of 1130 samples before 2000 to 55% of 106 in the 2000s.

Arsenic above the limit in Pinal County fell from 43% of 249 samples before 2000 to 27% of 157 in the 2000s.

Fluoride, 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 address

What this means

The contaminants most often above their limit here are arsenic (36% of 417 samples), nitrate (29% of 1,246 samples), and fluoride (8% of 1,469 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 Pinal County

1
Arsenic
36% of 417 local samples were above the limit.
2
Nitrate
29% of 1,246 local samples were above the limit.
3
Fluoride
8% of 1,469 local samples were above the limit.
4
Lead
<1% of 395 local samples were above the limit.
5
Coliform bacteria
Recommended for every private well, every year.
6
Radon
Median local reading is 363 pCi/L.
7
Chloride
Detected in 100% of local samples.
8
Volatile organic compounds (VOCs)
221 leaking underground storage tank sites on record locally.

Test your Pinal County well for arsenic, nitrate 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 $209 Already 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 Pinal County numbers, $29. Every line explained, ranked by what matters, with the fix for each.

Wells in Pinal County

8,502 domestic wells in Pinal County are on record with the state since 1970. the typical well is 460 feet deep (one in ten goes past 800 feet).

In a typical Pinal County well, the median yield is 12 gallons per minute, 5% of wells yield under 3 gallons per minute and usually need a storage tank.

498

1970s

853

1980s

987

1990s

1,328

2000s

343

2010s

209

2020s

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 Pinal County

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 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.

Well Water, ADHS
Licensed Commercial Drinking Water Laboratories, ADHS

Contamination sources on record in Pinal County

ADEQ records 221 leaking underground storage tank sites in Pinal County, among 229 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.

221: leaking underground storage tank sitesGasoline and heating oil that leaked from tanks move through groundwater as benzene, MTBE and other volatile organic compounds.
8: 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

Nitrate

Point-of-use reverse osmosis; Anion exchange; Distillation

Fluoride

Point-of-use reverse osmosis; Activated alumina; Distillation

Lead

Point-of-use reverse osmosis; Certified lead-removal carbon filter; Neutralizing filter to raise pH and stop leaching

Chloride

Point-of-use reverse osmosis; Distillation

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 lead

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 lead

Acid neutralizing filter

whole-house, at the point of entry, about $1,200

Raises pH so plumbing stops leaching lead and copper.

Free, no obligation

Get on the list for a free in-home water test in Pinal County

No water treatment company serves Pinal 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 Pinal County, and you get an email naming it first.

Common questions

How deep are wells in Pinal County?

The typical domestic well in Pinal County is 460 feet deep, based on 8,502 wells reported to the state since 1970. One in ten is deeper than 800 feet.

Is there arsenic in well water in Pinal County?

Arsenic was detected in 71% of 417 public well samples in Pinal County, and 36% 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 Pinal County?

The median radon level across 56 public samples in Pinal County was 363 pCi/L, with a high of 6,757 pCi/L. New Hampshire recommends treatment above 2,000 pCi/L.

How often should I test a private well in Pinal 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 Pinal 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: 8,325 samples in Pinal 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 12,570 people on private wells in Pinal 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): 16,384 well records in Pinal County, 8,502 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: 229 regulated sites located in Pinal 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.