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Water quality

Arizona water quality

Arizona public water systems are regulated by the Arizona Department of Environmental Quality (ADEQ) and generally meet federal standards. According to the EWG Tap Water Database and USGS hardness data, the most widely documented issues are naturally occurring arsenic in groundwater and some of the hardest water in the nation. Levels vary substantially by community and source, so local water-quality reports are the best reference for a given address.

Documented considerations

Arsenic

Arsenic occurs naturally in many Arizona aquifers, and EWG data shows several systems with levels below the EPA's 10 ppb legal limit but many times above the stricter EWG health guideline. Arsenic is a recognized carcinogen, making it Arizona's most documented health-related water concern.

Hardness

Arizona groundwater ranks among the hardest in the country, with the large majority of cities reporting hard or very hard water. Hardness causes scale and soap-scum problems but is not a health hazard.

Nitrate

According to ADEQ and EWG data, nitrate has been detected in some Arizona systems, particularly in agricultural and rural areas. Elevated nitrate above the EPA limit of 10 mg/L is a health risk, especially for infants.

Disinfection byproducts

Some Arizona systems report total trihalomethanes from chlorination of surface water, as noted in EWG database summaries.

EPA compliance snapshot

From the EPA ECHO Safe Drinking Water Act database, Arizona community water systems carrying one or more violations on record:

1,961
systems with a violation on record
101
with a health-based violation
57
flagged serious violators

Most common violation categories

  • Revised Total Coliform Rule (472)
  • Public Notice (273)
  • Chlorine (269)
  • Lead and Copper Rule Revisions (227)
  • Consumer Confidence Rule (216)
  • Nitrate (214)

Counts are public EPA ECHO figures. 'Health-based' means a system carries at least one health-based violation flag in ECHO. A violation on record is not a statement that current tap water is unsafe; most systems return to compliance. Always check your utility's Consumer Confidence Report for current status. Source: EPA ECHO, retrieved 2026-06-01.

Certified filters for Arizona's main concerns

FAQ

Does Arizona tap water have arsenic?
Yes, arsenic occurs naturally in many Arizona groundwater sources. According to the EWG Tap Water Database, a number of systems report arsenic below the EPA's 10 ppb legal limit but well above EWG's stricter health guideline, which is why arsenic is Arizona's most commonly cited water-quality concern.
Why is Arizona water so hard?
Arizona's groundwater moves through mineral-rich desert geology that dissolves high levels of calcium and magnesium. As a result, most Arizona cities have hard or very hard water, leading to scale buildup, spotting, and reduced appliance efficiency, though hardness is not a health risk.
Is it safe to drink tap water in Phoenix or Tempe?
Major Arizona city water systems generally meet EPA and ADEQ standards. Some areas show arsenic readings above health guidelines but below the legal limit, so residents concerned about arsenic or hardness may want to review their utility's report and consider certified treatment.

Sources

  1. EWG Review of Arsenic in Tap Water
  2. EWG Tap Water Database - Arsenic
  3. EPA - National Primary Drinking Water Regulations

Not sure how to read your local report? See our guide on reading a water quality report.