PFAS in Central Valley Tap Water

What PFAS are

PFAS (per- and polyfluoroalkyl substances) are a large family of manufactured chemicals used since the 1940s in nonstick, stain-resistant and water-repellent products and firefighting foam. They break down very slowly, which is why they’re called “forever chemicals.” You can’t see, smell or taste them.

The limits, in plain numbers

Federal (EPA). In April 2024 EPA set national drinking water limits: 4.0 parts per trillion (ppt) each for PFOA and PFOS; 10 ppt each for PFHxS, PFNA and HFPO-DA (GenX); and a “hazard index” of 1 for mixtures of PFHxS, PFNA, GenX and PFBS. Water systems must meet them starting in 2029. [U.S. EPA: PFAS National Primary Drinking Water Regulation] On May 18, 2026, EPA proposed moving the PFOA and PFOS deadline to 2031 and rescinding the limits for the other four. As of October 2026 those are proposals, not final rules. [U.S. EPA: Proposed PFOA and PFOS compliance extension rule]

California. The State Water Board uses notification levels (when a utility must tell its governing body) and response levels (when it’s recommended to take a source out of service or treat it). They are advisory, not enforceable limits. [California State Water Board: PFAS]

Sources: California State Water Board PFAS page (levels as listed Oct. 29, 2025); EPA PFAS rule page. PFBS levels date from March 5, 2021.

What our towns’ reports show

• Lathrop: PFOS in the combined distribution system averaged 15 ppt (13–17 ppt) in 2024 sampling, above the 4 ppt notification level and below the 40 ppt response level. Untreated city-well water averaged 147 ppt PFOS. PFHxS averaged 4 ppt and PFBS 4 ppt in the distribution system. [City of Lathrop 2025 Water Quality Report]
• Manteca: one well sampled Sept. 16, 2025 showed PFHxS at 7.5 ppt, above the 3 ppt notification level; PFOA ranged ND–2.8 ppt. The city says it is designing treatment at that well to remove PFAS. [City of Manteca 2025 Consumer Confidence Report]
• Turlock: the 2025 report explains PFAS but doesn’t list detections in its results tables. [City of Turlock 2025 Water Quality Report]
• Other towns: we didn’t find PFAS results in the 2025 reports for Patterson, Lodi, Escalon or Newman. Not listed doesn’t mean tested and not found. Check your own report, linked on each town page.

What reduces PFAS at home

RO reduces PFAS. According to the U.S. EPA, “High-pressure membranes, such as nanofiltration or reverse osmosis, have been extremely effective at removing PFAS.” EPA adds: “Research shows that these types of membranes are typically more than 90 percent effective at removing a wide range of PFAS, including shorter chain PFAS.” [U.S. EPA: Reducing PFAS in Drinking Water with Treatment Technologies]

That’s research on the technology. We don’t claim our unit is certified for PFAS. What we do: test your water, install an under-sink reverse osmosis system for drinking and cooking water, and change filters on schedule so it keeps working. A water softener or saltless system does not reduce PFAS.

Town pages with PFAS details

• RO in Lathrop & River Islands
• RO in Manteca
• Is my tap water safe?
• Take the water quiz

By Kyle C., Liquid Solutions Inc · Updated October 2026