PFAS in California Water: Testing & Removal

Few states carry a PFAS footprint as large as California's. The state posts one of the highest total detection counts in the entire national UCMR 5 sampling round, a figure driven by two forces at once: a population of nearly 40 million served by hundreds of separate utilities, and a dense concentration of contamination sources. The single biggest thread running through that record is firefighting foam. Tallies compiled in May 2020 identified roughly 62 military installations across the state with known or suspected PFAS releases, drawing on work by EWG, the California State Water Resources Control Board, and the EPA. Detections tend to cluster near Air Force bases, while municipal systems throughout the Central Valley and Southern California show their own scattered hits.

One consequence of all this is that no single map tells the whole California story. A utility or private well sitting downgradient of a base, an old industrial corridor, or an airport can read very differently from a supply just a few miles away. If your household depends on its own well or a small water system near any of those features, treat your situation as distinct from your neighbor's rather than assuming the two match. The state's sheer geographic range compounds the problem: a coastal Southern California district, an inland agricultural community, and a mountain foothill town each draw from different source water and sit near different histories of use, so statewide averages tell an individual homeowner very little about the tap in their own kitchen.

California's own thresholds and the 2024 federal limits

Ahead of federal rulemaking, California worked through notification and response levels rather than enforceable ceilings. Those include a PFOA notification level of 5.1 ppt and a PFOS notification level of 6.5 ppt, escalating to response levels of 10 ppt for PFOA and 40 ppt for PFOS, with additional figures set for PFHxS and PFBS. That state framework now sits alongside the federal maximum contaminant levels the EPA finalized in 2024: 4 parts per trillion apiece for PFOA and PFOS, and 10 ppt apiece for PFNA, PFHxS, and the GenX family. Public systems are obligated to sample and, where results run high, install treatment to satisfy those numbers.

How to test your water

People on a municipal supply can ask their utility for its PFAS monitoring data or open the annual Consumer Confidence Report. Private wells receive no such automatic scrutiny, which leaves a certified laboratory analysis, run under EPA Method 537.1 or 533, as the only trustworthy way to pin down your numbers. Sample first; let the results, not guesswork, drive the treatment decision. If your well sits within a few miles of a base, an airport, or an older industrial zone, that proximity is worth flagging to the lab so the analysis can be read in context. It is also reasonable to repeat the test every couple of years, since PFAS plumes in California groundwater can migrate slowly and a clean early reading does not guarantee the same result a few seasons later.

Three proven removal methods

Granular activated carbon (GAC): an established whole-house media that adsorbs longer-chain PFAS as water filters through the bed. Anion exchange resin: a charge-selective resin built to grab negatively charged PFAS, often the answer for stubborn short-chain compounds. Reverse osmosis (RO): a membrane that turns back a very broad slate of PFAS right at the tap. Whole-house GAC or anion units guard every fixture in the home, while an under-sink RO delivers a compact point-of-use option for drinking and cooking. A common California setup pairs a whole-house filter with an RO polish at the kitchen sink.

Recommended systems

Not sure which fits your home? Our PFAS water filter removal guide walks you through matching a method to your test results.