Arizona is a state where drinking water safety depends enormously on where your water comes from. Phoenix, Tucson, and the major metro areas treat and test their water extensively — though they face their own challenges with arsenic, chromium-6, PFAS from military bases, and hard water from the Colorado River (covered in our Phoenix and Tucson articles).
This article is about Arizona's private well users — an estimated 500,000+ Arizonans on private wells — who face a different and in some ways more serious set of risks. Arizona groundwater contains naturally elevated concentrations of arsenic, uranium, fluoride, radium, and other contaminants derived from the state's volcanic and sedimentary geology. And in an arid state where the water table has dropped dramatically due to decades of agricultural and population growth, some of this deep aquifer water is being brought to the surface for the first time.
Arizona ranks among the states with the highest rates of arsenic in private wells. The geology that produces the Grand Canyon, Arizona's volcanic mountains, and its rich mineral deposits also produces groundwater that is chemically complex.
The Geology of Arizona's Groundwater Problem
Arizona sits atop a patchwork of aquifer systems with very different chemical profiles. The contamination concerns aren't industrial — they're mostly natural, derived from the rock formations that the water moves through over decades or centuries.
Arsenic: Volcanic rocks and sulfide minerals throughout Arizona's geology naturally leach arsenic into groundwater. The EPA's MCL for arsenic in public water systems is 10 ppb — but surveys of Arizona private wells have found arsenic concentrations ranging from background levels to 100+ ppb in some areas. The EPA's MCL was itself lowered from 50 ppb to 10 ppb in 2001 specifically because the previous standard was considered too permissive. EWG's health guideline is 0.004 ppb — based on a 1-in-1 million cancer risk from lifetime exposure.
Arsenic is a known human carcinogen (IARC Group 1). Long-term exposure at elevated concentrations increases risk of skin, bladder, lung, and kidney cancers. At the concentrations found in some Arizona wells — sometimes 5–10x the MCL — this is a genuine, serious health concern.
Uranium: Arizona's uranium deposits (the state has significant uranium ore reserves) contribute uranium to groundwater in many areas. The EPA MCL for uranium is 30 micrograms per liter (µg/L). Uranium exposure from drinking water is associated with kidney damage (nephrotoxicity) as well as radiation-related cancer risk. Areas near historic uranium mining — the Colorado Plateau in northern Arizona (Grand Canyon region, Coconino County) — have particularly elevated uranium in some groundwater systems.
Radium: Naturally occurring radioactive materials (NORM) including radium-226 and radium-228 are found in Arizona groundwater, particularly in Maricopa, Pinal, Pima, and Yavapai counties. The EPA regulates combined radium 226+228 at 5 pCi/L. Radium is a decay product of uranium and thorium in rock formations.
Fluoride: Arizona has some of the highest naturally occurring fluoride levels in US groundwater — ironic given that most cities deliberately add fluoride to achieve 0.7 mg/L, while some Arizona wells naturally contain 2–5+ mg/L, well above the EPA's secondary limit of 2 mg/L. High-fluoride well water causes severe dental fluorosis and, at very high levels (4+ mg/L), skeletal fluorosis — a serious bone disease. This is a risk primarily in Navajo Nation territory and rural areas of southern and central Arizona.
Chromium-6: Both naturally occurring (from ultramafic rock formations) and from industrial sources, chromium-6 is present in Arizona groundwater. The Arizona Department of Environmental Quality monitors for chromium-6, and it's been detected in some wells above EWG's 0.02 ppb health guideline.
The Military PFAS Layer
On top of the geological contamination, Arizona has one of the densest concentrations of military installations in the country — and military use of AFFF (aqueous film-forming foam) has contaminated groundwater near dozens of bases nationwide.
Affected areas and bases:
- Luke Air Force Base (Glendale/northwest metro Phoenix): PFAS-contaminated groundwater has affected private wells and smaller municipal systems in the surrounding area
- Davis-Monthan Air Force Base (Tucson): Covered in our Tucson article — significant PFAS plume affecting southeast Tucson
- Yuma Proving Ground / Marine Corps Air Station Yuma: Remote but significant PFAS footprint
- Fort Huachuca (Sierra Vista): PFAS monitoring ongoing; municipal system actively treating
- Williams Gateway (Mesa/Gilbert area): Former Williams AFB, now Phoenix-Mesa Gateway Airport; PFAS contamination in surrounding groundwater
Well owners within several miles of these facilities — particularly within 5 miles and in the downgradient direction — should test specifically for PFAS.
What Arizona Well Owners Should Test For
Recommended test panel for Arizona private wells:
The standard ADWR/ADEQ recommendation is to test at minimum when first moving in, then every 1–3 years for bacteriological indicators and more frequently after any change in taste, smell, or color. But for Arizona specifically, a comprehensive inorganic and radiological test is warranted given the geological risks.
The essential test panel:
- Arsenic (priority 1 — highest risk, most widespread in AZ)
- Nitrates (risk from agricultural areas and septic systems)
- Coliform bacteria (baseline sanitation check)
- pH and hardness (affects filter performance and pipe corrosion)
- Uranium (particularly near Colorado Plateau, Coconino County)
- Radium-226/228 (combined radiological panel)
- Fluoride (particularly in Navajo Nation area and southern/central AZ)
- PFAS panel (if within 10 miles of military installation)
- Total dissolved solids (TDS) (general water quality indicator)
Recommended testing services:
- Arizona Department of Environmental Quality (ADEQ) maintains a certified laboratory list: azdeq.gov
- Tap Score Well Water Test (~$175–250) — comprehensive at-home sampling kit with certified lab analysis; recommended for comprehensive panel
What Filters Work for Arizona Well Water
Arizona's geological contamination profile — arsenic, uranium, radium, fluoride, chromium-6 — is almost uniquely suited to RO filtration. RO removes all of these through the membrane rejection process. This is not a situation where a carbon pitcher will solve the problem.
The filtration hierarchy for Arizona well water:
Level 1: Reverse Osmosis (Under-Sink) — Essential for High Contaminant Levels
An NSF 58 certified under-sink RO system handles the core Arizona well water concerns:
- Arsenic: 95–99% removal (verified by NSF 58 certification)
- Uranium: RO removes uranium effectively (typically 90%+)
- Radium: RO removes 90%+ of dissolved radium
- Fluoride: 85–95% removal
- Chromium-6: 90%+ removal
- PFAS: 95%+ removal
- Nitrates: 85–95% removal
This is why RO is the standard recommendation for Arizona well users with geological contaminant concerns.
- APEC ROES-50 (~$215) — NSF 58 certified; the standard recommendation; WQA Gold Seal; removes all priority Arizona well contaminants; 5-stage; standard 10" filter replacements; ~1–3 hour DIY install
- iSpring RCC7AK (~$219) — adds alkaline remineralization; important in Arizona where RO will strip heavily mineralized well water; better post-filtration taste
- Waterdrop G3P600 (~$450–500) — tankless design; 600 GPD flow rate; better for households with higher daily water consumption; more expensive but faster delivery and no tank
Level 2: Pre-filtration for High Sediment or Iron
Many Arizona wells — particularly in rural areas, older properties, or areas with reddish/orange water — have elevated sediment, iron, or manganese. These can foul an RO membrane quickly if not pre-filtered.
If your water has visible sediment, iron staining, or reddish color: Install a whole-house sediment filter (5–10 micron) and iron filter upstream of your RO system. The RO is then protected and will last significantly longer.
What to look for: Iron content above 0.3 mg/L should be pre-treated before RO. You can test for iron with a basic well water test kit or home colorimetric test.
Level 3: Whole-House vs. Point-of-Use
For drinking and cooking water, under-sink RO at the kitchen tap is the standard solution and covers the main exposure routes (drinking, cooking, infant formula).
The case for whole-house filtration in Arizona:
- If you have elevated arsenic or fluoride, shower/bath inhalation and skin contact is a secondary exposure route (less significant than ingestion but real)
- For very high arsenic levels (50+ ppb), whole-house treatment may be warranted
- Whole-house RO is expensive ($1,000–3,000+ installed) — most Arizona well owners use kitchen under-sink RO for drinking and accept the tap for other uses
A whole-house sediment + carbon filter combination (no RO) is a good complement to kitchen RO: it protects appliances from sediment and reduces aesthetic issues without the cost of whole-house RO.
Special Situations
Navajo Nation and Tribal Areas
Navajo Nation has a unique and severe water quality challenge. A 2020 survey by the Navajo Nation Environmental Protection Agency found that approximately 30–40% of homes lack access to piped water, with many relying on unregulated hauled water or untreated surface and groundwater. Uranium contamination from historical mining on the Colorado Plateau — many unreclaimed uranium mines are on Navajo land — creates elevated uranium in some water sources.
If you're in a Navajo Nation or tribal community, the water quality concerns are potentially severe and the standard private well advice applies with extra urgency. Testing through the Navajo EPA or IHS (Indian Health Service) environmental programs is the starting point.
Agricultural Well Users
Arizona's irrigated agriculture uses enormous volumes of groundwater, and irrigation return flows can carry agricultural chemicals back into the water table. Well users near agricultural operations should add nitrates, pesticides, and herbicides (atrazine, simazine) to their standard test panel. RO addresses nitrates; activated carbon addresses most common pesticides.
Resources
- Arizona Department of Environmental Quality (ADEQ) well water guidance: azdeq.gov/water/drinking/private-wells
- Arizona Department of Water Resources (ADWR): azwater.gov
- PFAS military contamination map: epa.gov/pfas/drinking-water-health-advisories-pfoa-pfos
- Navajo EPA water program: navajoepa.org
- NSF certified RO systems: info.nsf.org/Certified/dwtu
Related Articles
- Arsenic in Drinking Water: The Well Water Risk Most People Don't Test For
- Phoenix, Arizona Water Quality 2026: Arsenic, Hard Water, and Colorado River Concerns
- Tucson, Arizona Water Quality 2026: Davis-Monthan PFAS Plume and What Residents Can Do
- PFAS in Drinking Water: What It Is, Where It's Found, and How to Filter It
- Best Water Filter for Well Water: What Private Well Owners Actually Need
- Fluoride in Drinking Water: What It Is, What the Research Shows, and How to Remove It
Sources: EPA: Arsenic in Drinking Water · USGS: Arsenic in Groundwater of the Western United States · Arizona Department of Environmental Quality: Private Well Program · EPA: PFAS Strategic Roadmap / Military Installations · MPCA: PFAS Water Quality Criteria, 2025 · Indian Health Service: Arizona Water Quality Programs · EWG: Arizona Tap Water · NSF Certified Products Database