Arizona's PFAS Monitoring Data: What the EPA UCMR5 Results Show for Phoenix Metro Water Utilities

Between 2023 and 2025, water utilities across Arizona participated in the EPA's Unregulated Contaminant Monitoring Rule 5, known as UCMR5, the most comprehensive federal survey of per- and polyfluoroalkyl substances in public drinking water ever conducted in the United States (epa.gov/dwucmr). UCMR5 required every community water system serving more than 3,300 people to test finished drinking water for 29 PFAS compounds and to report all results to a publicly searchable federal database. In April 2024, the EPA followed that data collection with the first legally enforceable National Primary Drinking Water Regulation for PFAS, setting Maximum Contaminant Levels for six compounds and establishing a compliance deadline of April 2029 (epa.gov/sdwa/pfas-drinking-water-regulation). For Phoenix metro homeowners, the combined picture from UCMR5 monitoring and the new MCL rule raises a direct question: what did Arizona utilities actually detect, and what does federal law now require them to do about it? This article explains the program, where to find your utility's results, and what the data means for households in Maricopa County.

What UCMR5 requires water utilities to test

UCMR5 is an EPA program that collects occurrence data for contaminants not yet subject to federal drinking water standards, so the EPA can decide whether regulation is warranted (epa.gov/dwucmr). The fifth cycle, which ran from January 2023 through December 2025, focused specifically on PFAS because most compounds in this chemical family lacked any monitoring requirement under the Safe Drinking Water Act prior to 2023. Every community water system serving more than 3,300 customers was required to test. Systems serving between 25 and 3,299 people were sampled by the EPA using a statistical selection process. Utilities had to collect samples at the entry point to the distribution system and at representative points within the distribution system. All results were submitted to the EPA and are now searchable through the EPA's UCMR Data Finder tool at epa.gov/dwucmr. Arizona utilities subject to UCMR5 include the major Phoenix metro providers: Phoenix Water Services, Scottsdale Water, Mesa Utilities, Chandler, Gilbert, Tempe, Glendale, and several smaller systems. To see your utility's exact reported values, enter the system name or your state in the UCMR Data Finder and download the results table. The Arizona Department of Environmental Quality also tracks PFAS monitoring at azdeq.gov/pfas_dw and maintains state-level resources for interpreting utility data.

EPA's enforceable PFAS limits, finalized in April 2024

On April 10, 2024, the EPA published the final National Primary Drinking Water Regulation for PFAS. The rule creates six enforceable MCLs and applies a separate hazard index calculation for PFAS mixtures (epa.gov/sdwa/pfas-drinking-water-regulation). Every public water system in the United States must meet these limits by April 2029.

• PFOA (perfluorooctanoic acid): 4 parts per trillion (ppt)
• PFOS (perfluorooctane sulfonate): 4 parts per trillion (ppt)
• PFNA (perfluorononanoic acid): 10 parts per trillion (ppt)
• PFHxS (perfluorohexane sulfonate): 10 parts per trillion (ppt)
• HFPO-DA, commonly called GenX: 10 parts per trillion (ppt)
• Hazard Index for PFNA, PFHxS, HFPO-DA, and PFBS combined: 1.0 (unitless sum of individual concentration divided by MCL)

The 4 ppt limit for PFOA and PFOS represents a significant tightening from the previous 70 ppt health advisory that had been in place since 2016. The EPA states in its rulemaking that there is no measured safe level for PFOA or PFOS based on current epidemiological evidence, and that the MCLs were set as close to the maximum feasible level that treatment technology can reliably achieve (epa.gov/sdwa/pfas-drinking-water-regulation). The mixture hazard index is a new regulatory tool designed to account for combined exposure when a utility detects several PFAS compounds below their individual MCLs but at concentrations that together represent a meaningful combined risk.

How Phoenix metro utilities have responded to UCMR5 and the 2024 MCL rule

Under the Safe Drinking Water Act, utilities that detect PFAS at or above the new MCLs by the compliance date of April 2029 must notify customers, provide public information about health risks, and implement treatment or source water changes to bring concentrations into compliance. If a utility detects PFAS above MCLs and cannot achieve compliance through blending or source switching, it must install treatment capable of reducing PFAS to compliant levels (epa.gov/sdwa/pfas-drinking-water-regulation). The treatment methods the EPA identifies as Best Available Technology for PFAS removal include granular activated carbon filtration, high-pressure membrane systems such as nanofiltration and reverse osmosis, and anion exchange resins. These are capital-intensive investments. Phoenix draws water primarily from the Salt and Verde rivers via the Salt River Project and from the Colorado River via the Central Arizona Project. Both sources have been monitored for PFAS. Utilities using Colorado River water face elevated scrutiny because the river has documented PFAS inputs from upstream industrial and military sources at multiple locations. UCMR5 data allows direct comparison of which Arizona utilities detected PFAS and at what concentrations. Homeowners can view those results now, before the 2029 compliance deadline, using the EPA search tools described below.

How to look up your utility's PFAS data

The EPA makes UCMR5 results publicly available through two tools. The first is the UCMR Data Finder at epa.gov/dwucmr, which allows you to search by state, water system name, or public water system ID number. Download the results file for your utility and look for any detections across the 29 PFAS compounds tested. A detection does not automatically mean a violation: compare the detected concentration to the MCLs listed above to assess where your utility stands relative to the April 2029 compliance deadline. The second tool is the EPA's Safe Drinking Water Information System (SDWIS), also accessible from epa.gov/dwucmr, which records formal violations, enforcement actions, and monitoring history going back decades. The Arizona Department of Environmental Quality maintains a state-level PFAS in drinking water page at azdeq.gov/pfas_dw that links to Arizona-specific monitoring data and provides contact information for state drinking water staff who can answer questions about specific utilities. Additionally, each utility must publish an annual Consumer Confidence Report, or CCR, mailed or emailed to customers each July and available on the utility's website. Starting with reporting years 2026 and beyond, CCRs will be required to include PFAS data consistent with the new MCL rule. For years 2023 through 2025, check whether your utility voluntarily included UCMR5 results in its CCR or published a separate PFAS update on its website.

What Arizona homeowners can do right now

Compliance deadlines apply to utilities, not to the water at your tap today. Homeowners who want to reduce PFAS exposure before 2029, or who have a private well not covered by UCMR5, have point-of-use options available now. The EPA identifies reverse osmosis systems certified to NSF/ANSI Standard 58 as the treatment method with the strongest verified reduction for PFOA and PFOS at the point of use (epa.gov/water-research/identifying-drinking-water-filters-certified-reduce-pfas). Granular activated carbon filters with long contact time also reduce PFAS, but performance varies by system design and cartridge type. Standard pitcher filters and most refrigerator filters are not certified for PFAS reduction. A water test at your tap is the starting point. Testing can confirm whether PFAS compounds are detectable at your specific address and at what concentrations, particularly if your home has an older plumbing system or is served by a smaller utility not subject to UCMR5 mandatory testing.

• Look up your utility's UCMR5 results at epa.gov/dwucmr using the UCMR Data Finder
• Download your most recent Consumer Confidence Report from your utility's website and check for PFAS data
• Review ADEQ's Arizona-specific PFAS monitoring resources at azdeq.gov/pfas_dw
• If you rely on a private well, contact ADEQ or a certified laboratory for PFAS testing, as private wells are not covered by UCMR5 or the MCL rule
• If PFAS are detected at your tap, consider a reverse osmosis system certified to NSF/ANSI Standard 58 for point-of-use reduction
• Schedule a free professional water test to measure PFAS alongside hardness, TDS, chloramine, and other parameters relevant to your Phoenix metro household