Worst Water Quality Cities in the US (2025)
Which cities have the hardest, most contaminated tap water?
Hardest water
The hardest municipal water is concentrated in the desert Southwest and Great Plains. Cities like San Antonio, Phoenix, Las Vegas, Indianapolis, and El Paso routinely test above 200 PPM. At these levels, a water softener is essential for protecting plumbing and appliances. See the full city rankings.
Highest PFAS
PFAS contamination is worst near military bases (AFFF firefighting foam), industrial sites, and chemical manufacturing. Cities in North Carolina, Michigan, New Jersey, and Colorado have some of the highest detected levels. The 2024 EPA standard of 4 ppt means many cities are now technically non-compliant.
Worst lead infrastructure
Cities with the oldest water infrastructure (built before 1940) and highest rates of lead service lines include Chicago, Pittsburgh, Newark, and older northeastern cities. Lead is a building-level issue, so testing your individual tap is critical regardless of city averages.