PFAS in California drinking water

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What PFAS are

PFAS (per- and polyfluoroalkyl substances) are a large family of man-made chemicals used since the mid-1900s in non-stick coatings, stain- and water-resistant fabrics, food packaging and some firefighting foams. They are called "forever chemicals" because their carbon-fluorine bonds break down extremely slowly in the environment and in the body. In drinking water they are measured in tiny amounts, nanograms per liter (ng/L), which is the same as parts per trillion (ppt).

Groundwater near industrial sites, airports and military bases where firefighting foam was used has been a common source of detections nationally. Whether PFAS show up in your tap water depends on your utility's sources and treatment, which is why a ZIP-level check is the right starting point.

California's PFAS levels

California regulates PFAS through notification levels (NL) and response levels (RL) set by the State Water Board's Division of Drinking Water. Per the board's PFAS drinking water page, the current levels are:

What these mean: an NL is a non-regulatory, health-based advisory level. When a system detects a PFAS above its NL, the board's rules require it to notify its governing body and the board recommends informing customers. An RL is higher; when a system under a monitoring order exceeds it, the system must take the source out of service, treat the water, or provide public notification. Response-level exceedances for PFOA, PFOS, PFHxS and PFHxA are judged on a running annual average of quarterly samples; PFBS uses a single confirmed sample. The board also has PFAS monitoring orders that require many systems to sample their sources; its PFAS monitoring FAQ explains how those orders work.

How the federal PFAS rule fits in

In April 2024 the U.S. EPA finalized the first national enforceable PFAS drinking water limits, including maximum contaminant levels of 4.0 ppt each for PFOA and PFOS. EPA has since announced that it intends to keep the PFOA and PFOS limits, extend the compliance timeline, and reconsider the limits for several other PFAS. Because that process is ongoing, check EPA's PFAS drinking water page for the current status rather than relying on any summary, including this one.

For a California homeowner the practical point is that both state advisory levels and federal limits are now in the single-digit parts-per-trillion range for PFOA and PFOS, so any measurable detection is worth understanding.

How to find out whether your water has PFAS

1. Run your ZIP and confirm the utility on your bill. TapCheck shows PFAS detections where they are in the public monitoring data we use.
2. Read your Consumer Confidence Report. Detected PFAS are typically listed with unregulated or notification-level constituents.
3. Check the state's records. The State Water Board publishes PFAS sampling results; links are on its PFAS page, and system results are searchable in Drinking Water Watch.
4. Understand the limits of the data. Not every source is sampled for every PFAS on the same schedule, and a "not detected" result only means below the lab's reporting level.

Home filters that reduce PFAS

Certified products are the safest bet. NSF/ANSI 53 and NSF/ANSI 58 include a PFOA/PFOS reduction claim, and the NSF certified products listings let you search by contaminant. In practice:

• Reverse osmosis (RO) under-sink systems certified for PFOA/PFOS are a common choice for drinking and cooking water.
• Activated carbon pitchers, faucet mounts and under-sink cartridges can reduce PFOA/PFOS when certified for it; performance depends on the product and on changing cartridges on schedule.
• Whole-house systems exist, but most PFAS exposure from water is through drinking and cooking, so point-of-use treatment is where most homeowners start.

Whatever you buy, change filters on the manufacturer's schedule; a spent carbon cartridge stops reducing PFAS. The filter basics page explains carbon vs reverse osmosis.

PFAS and other contaminants

PFAS often come up alongside other California concerns. If your report shows them, also look at chromium 6 and hardness, since an RO system addresses several issues at once while a softener addresses only hardness.

Related guides

• Hard water in California
• Chromium 6 in California water
• How to check tap water by ZIP
• City water guides
• Regional water guides

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