Maricopa County, Arizona: drinking water report. Maricopa County covers the Phoenix metro and surrounding communities, with a population of roughly 4.5…
Maricopa County covers the Phoenix metro and surrounding communities, with a population of roughly 4.5 million – making it the fourth most populous county in the country. Water comes from three sources: the Salt River Project reservoirs, the Central Arizona Project canal delivering Colorado River water, and groundwater wells tapping the Salt River Valley aquifer. Summer temperatures regularly exceeding 115°F create conditions that accelerate disinfection byproduct formation in treated water, a challenge unique to desert systems.
PFAS contamination in Maricopa County is concentrated around military installations. Luke Air Force Base in the West Valley and the former Williams Air Force Base in Mesa have both been identified as PFAS sources, with firefighting foam residues detected in surrounding monitoring wells. The Arizona Department of Environmental Quality has conducted supplemental sampling, and the EPA's UCMR5 data confirms detections across multiple public water systems in the county.
Water hardness is another defining characteristic. According to USGS assessments, Central Arizona Project water delivered to Maricopa County averages over 300 mg/L total dissolved solids – well above the national median for municipal supplies. While hardness is not a health hazard, it affects taste, causes scale buildup, and can interact with treatment chemicals in ways that alter the final contaminant profile at your tap.
Water quality across Maricopa County varies by municipality and by the specific mix of sources feeding your area. West Valley communities near Luke AFB face different risks than East Valley towns drawing primarily from SRP reservoirs.
Check your water to see what has been detected in your service area. For PFAS, activated carbon or reverse osmosis filters are the most effective household options. For hardness and TDS concerns, a whole-house softener may also help. Our water filter guide covers both scenarios. Grab your detailed report for multi-year trends, and see our Arizona page for statewide patterns.