Los Angeles County, California: drinking water report. Los Angeles County is the most populous county in the United States, home to over 10 million
Los Angeles County is the most populous county in the United States, home to over 10 million residents spread across 88 cities and dozens of unincorporated communities. Water here comes from a patchwork of providers – LADWP serves the city, but dozens of smaller utilities, mutual water companies, and special districts handle the rest. That fragmentation means water quality varies block by block in ways most residents never realize. The county draws from the Colorado River, State Water Project, local groundwater basins, and recycled water, with each source carrying a distinct contaminant profile.
The EPA's UCMR5 monitoring program has detected PFAS compounds across multiple water systems in Los Angeles County. According to the California State Water Resources Control Board, over 40 public water systems in the county have reported detectable PFAS levels, with some San Fernando Valley wells exceeding the state's notification level of 5.1 ppt for PFOA. Groundwater contamination near former aerospace facilities and military sites – including the Santa Susana Field Laboratory and several Superfund locations – adds legacy industrial chemicals to the mix.
The county also faces elevated levels of disinfection byproducts in systems treating warm surface water, and chromium-6 remains a concern in several groundwater basins. A 2023 analysis by the Environmental Working Group found that 78% of tested water systems in LA County had at least one contaminant exceeding their health guidelines.
With so many water providers operating independently, your first step is figuring out which system actually serves your home. A house in Pasadena draws from a completely different supply than one in Compton or Malibu.
We recommend starting with our free lookup tool – check your water by entering your ZIP code to see which contaminants have been detected in your specific service area. If PFAS or chromium-6 show up, a reverse osmosis or activated carbon filter certified to NSF/ANSI 53 or 58 will handle both. Our water filter guide ranks systems by actual lab-tested removal rates, not manufacturer claims.
For a full breakdown of historical trends and current readings, pull your detailed report. And for statewide patterns across California's water systems, visit our California page.