<p data-bluf="true"> EPA's Fifth Unregulated Contaminant Monitoring Rule (UCMR5) required the largest public water systems in Arizona to test for 29 PFAS compounds between 2023 and 2025. Across the Phoenix metro area, results vary significantly by utility and water source. The City of Phoenix, City of Mesa, City of Scottsdale, and City of Glendale did not exceed the EPA's new 4 parts per trillion (ppt) Maximum Contaminant Level for PFOA or PFOS, according to EPA utility rating data at waterutilityreport.com (citing UCMR5 records). Gilbert (Town of) recorded PFOS at 9.8 ppt, more than twice the federal limit, serving approximately 247,600 residents. City of Avondale recorded PFOA at 13.5 ppt. Statewide, 27 Arizona utilities exceeded the final MCL, serving roughly 1.7 million people (mapscaping.com, citing EPA PFAS Analytic Tools). This article compiles the available public data for the Phoenix metro, explains the regulatory timeline, and outlines what the readings mean for homeowners considering point-of-use filtration. </p>
Request a free water test in the Phoenix area to get an independent read on what is in your specific tap water before making any treatment decision.
The Fifth Unregulated Contaminant Monitoring Rule is the federal framework under which EPA required public water systems serving more than 3,300 customers to test for PFAS compounds from January 2023 through December 2025. Results are publicly available through the EPA UCMR5 Data Finder at epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule-data-finder.
UCMR5 data became the factual foundation for the EPA's April 10, 2024 final rule establishing the first enforceable federal Maximum Contaminant Levels for PFAS in drinking water (epa.gov/sdwa). The rule set:
| Compound | MCL | Notes |
|---|---|---|
| PFOA (perfluorooctanoic acid) | 4 ppt | Individual limit |
| PFOS (perfluorooctane sulfonate) | 4 ppt | Individual limit |
| PFHxS + PFNA + HFPO-DA (GenX) | 10 ppt (hazard index) | Combined limit |
| PFBS | No individual MCL | Monitored but not individually capped |
Source: EPA National Primary Drinking Water Regulation for PFAS, April 2024.
Compliance deadline: April 26, 2029. Until then, utilities must notify customers within 30 days of a confirmed MCL exceedance but are not yet in violation of the rule.
The table below summarizes publicly available UCMR5 findings for major Phoenix metro water systems. Data are drawn from EPA UCMR5 records as compiled by waterutilityreport.com (which cites EPA SDWIS and UCMR5 records directly) and the mapscaping.com Arizona PFAS analysis (citing EPA PFAS Analytic Tools). The EPA UCMR5 Data Finder at epa.gov is the primary source for individual utility records.
| Utility | Pop. Served | PFAS MCL Status | Highest Reading (ppt) | Compound |
|---|---|---|---|---|
| City of Phoenix | 1,695,000 | No MCL exceedance | Below MCL | n/a |
| City of Mesa | 466,000 | No MCL exceedance | Below MCL | n/a |
| Town of Gilbert | 247,600 | **Exceeds MCL** | 9.8 | PFOS |
| City of Chandler | 247,328 | Detected, monitoring | Data in UCMR5 finder | varies |
| City of Scottsdale | 241,361 | No MCL exceedance | Below MCL | n/a |
| City of Glendale | 234,766 | No MCL exceedance | Below MCL | n/a |
| City of Avondale | 83,001 | **Exceeds MCL** | 13.5 | PFOA |
| USAF Luke AFB | 8,976 | **Exceeds MCL** | 11.3 | PFOS |
Sources: waterutilityreport.com (citing EPA UCMR5/SDWIS); mapscaping.com Arizona PFAS map (citing EPA PFAS Analytic Tools); Gilbert water quality page at gilbertaz.gov; Avondale regulatory compliance page at avondaleaz.gov.
Three important caveats:
The primary driver is source water: where a utility draws its water and what is upstream.
Surface water from the Colorado River and Salt River tends to carry lower PFAS loads because agricultural and industrial PFAS inputs to these rivers have historically been lower than near military or industrial sites. The City of Phoenix, Mesa, Scottsdale, and Glendale all rely substantially on Salt River Project (SRP) and Central Arizona Project (CAP) Colorado River deliveries, treated at large surface-water plants.
Groundwater wells near military or industrial sites carry higher risk. The Town of Gilbert draws from wells in areas downgrade of PFAS-laden firefighting foam (AFFF) historically used at military and airport sites. Luke Air Force Base is a documented PFAS source: AFFF use for aircraft fire training deposited PFOS and PFOA into the subsurface, and the base water system showed PFOS at 11.3 ppt. Avondale also relies in part on groundwater from areas with documented AFFF contamination history.
The Arizona Department of Environmental Quality (ADEQ) maintains a PFAS drinking water program at azdeq.gov/PFAS_DW that includes maps of known contamination sites and funding assistance for affected utilities.
Gilbert, Avondale, and Luke AFB must achieve compliance with the 4 ppt MCL by April 2029. The treatment options utilities typically deploy include:
Granular activated carbon (GAC): Proven effective at reducing PFAS in large-scale municipal treatment. GAC systems are costly to install and require regular media replacement. Effectiveness varies by PFAS compound.
High-pressure membrane systems (nanofiltration or reverse osmosis at utility scale): Very high removal efficiency for PFAS but more expensive than GAC per gallon treated. Some utilities, particularly smaller ones, are choosing point-of-entry RO over GAC because of lower capital cost per household served.
Ion exchange resin: Single-use anion exchange resins developed specifically for PFAS are increasingly deployed at the well-head level, particularly where only specific well sources are affected.
ADEQ has allocated $5 million in state funding plus Bipartisan Infrastructure Law federal money to help small and disadvantaged water systems cover treatment costs (azdeq.gov).
Utilities have until 2029 to comply. That window leaves residents in affected service areas receiving water that currently exceeds the final federal limit. The gap between now and 2029 is not a regulatory free pass; it is the buildout period utilities need to install treatment infrastructure.
For homeowners who want to reduce PFAS exposure before municipal treatment is upgraded, the documented option is point-of-use reverse osmosis certified to NSF/ANSI Standard 58. NSF International independently tests and certifies that certified RO units remove PFOA, PFOS, and other PFAS compounds to the verified levels listed on the certification. The NSF/ANSI 58 standard and certified product listings are maintained at nsf.org.
Key points when evaluating an RO system for PFAS:
Whole-house filtration using PFAS-rated GAC media can reduce PFAS at all taps. These systems use more carbon media than point-of-use units, and the media requires periodic replacement. Point-of-use RO remains more cost-effective for most households when the goal is reducing PFAS in drinking and cooking water specifically.
Every Phoenix metro resident can look up their utility's individual UCMR5 sample results at the EPA UCMR5 Data Finder: epa.gov/dwucmr/fifth-unregulated-contaminant-monitoring-rule-data-finder.
Search by state (Arizona) and filter by your water system name. Results show each analyte, each sample date, and the measured concentration. Your utility's public water system ID (PWSID) is on your annual Consumer Confidence Report (CCR), which Arizona utilities are required to publish by July 1 each year.
If your utility detected any PFAS compound at or above EPA's minimum reporting level, you will see a non-zero result in the data. A reading below 4 ppt for PFOA or PFOS means the sample did not exceed the final MCL. A reading above 4 ppt means it did, and your utility is required to notify customers and develop a treatment plan.
UCMR5 only covers public water systems. About 18% of Arizona residents rely on private wells, which fall outside federal utility compliance monitoring (waterutilityreport.com, citing EPA data). Private well owners near Luke AFB, Williams Gateway Airport, or any former industrial site with documented PFAS use should test their well independently. Arizona provides a list of certified testing laboratories through ADEQ's website.
City of Phoenix water did not exceed the EPA Maximum Contaminant Level of 4 parts per trillion for PFOA or PFOS under UCMR5 monitoring (2023-2025). Phoenix draws primarily from the Colorado River via the Central Arizona Project and Salt River Project surface water, which undergoes treatment at City-operated plants. Individual UCMR5 records for the City of Phoenix (PWSID AZ0407025) are searchable through the EPA UCMR5 Data Finder at epa.gov.
Under EPA's UCMR5 monitoring program, Gilbert (Town of) recorded PFOS at 9.8 parts per trillion, exceeding the 4 ppt MCL finalized in April 2024. City of Avondale recorded PFOA at 13.5 ppt, also above the MCL. Luke Air Force Base recorded PFOS at 11.3 ppt. Across Arizona, 27 water utilities exceeded the 4 ppt MCL for PFOA or PFOS, serving roughly 1.7 million people, according to an analysis of EPA UCMR5 records published by mapscaping.com citing the EPA PFAS Analytic Tools database.
On April 10, 2024, the EPA finalized the National Primary Drinking Water Regulation for PFAS, setting a Maximum Contaminant Level of 4 parts per trillion (ppt) for PFOA and 4 ppt for PFOS individually. The rule also sets a combined hazard index limit for PFHxS, PFNA, and HFPO-DA (GenX chemicals). Public water utilities have until 2029 to comply. The final rule is documented at epa.gov/sdwa.
Yes. Reverse osmosis systems certified to NSF/ANSI Standard 58 are independently verified to reduce PFOA, PFOS, and other PFAS compounds in drinking water. An under-sink RO system treats water at the point of use, typically the kitchen tap, which covers the primary drinking and cooking exposure pathway. Look for the NSF mark and confirm the unit lists PFAS (or PFOA/PFOS) as a certified reduction contaminant.
Water utilities that exceed the new MCL for PFOA, PFOS, or the combined compounds have until April 26, 2029 to comply, per the EPA's final PFAS NPDWR rule published April 2024. ADEQ holds primary enforcement authority in Arizona and is coordinating compliance assistance through its PFAS drinking water program at azdeq.gov.
---
Schedule a free water quality consultation in the Phoenix area to discuss your options before the 2029 compliance window closes.
Schedule a free water test and get personalized recommendations for your home.
Continue learning about water quality and treatment
Scottsdale draws nearly all its water from the Central Arizona Project on the Colorado River, water that is very hard and high in TDS. Here is what 2025 public data shows about Scottsdale tap water quality and what homeowners should consider for filtration and softening.
A data analysis of chromium-6, contaminants, and water quality in the Coachella Valley using 2024 Consumer Confidence Reports from Coachella Valley Water District and Desert Water Agency. Covers CVWD's 9.4 ppb chromium-6 average against California's new 10 ppb MCL.
Gilbert tap water tests at 13 to 17 grains per gallon and up to 700 mg/L TDS in summer. This guide covers what is in Gilbert water, what a free home test measures, and which treatment options work best in the East Valley.
