PFAS rule dates: 3 milestones and two 4 ppt limits

Start with the dates and figures

EPA's PFAS rule timeline includes a proposal, a final rule and an announcement of intent to retain 4 ppt levels for PFOA and PFOS.

• Check whether a rule announcement describes a proposal, a final regulation or an intent.
• Confirm your water report's chemicals, units and reporting limit.
• Match filter certification listings to the chemicals in your results.

Most people meet the PFAS rule through a headline, a filter advertisement, or a notice from their water provider. Each of those may use different dates and numbers, and some blur the difference between a proposal and a final rule. This post draws the dates and figures from the Water Quality Association's PFAS portal for water treatment professionals, which summarizes EPA's rulemaking. Read the numbers first. Then judge any filter claim against them.

Start with what PFAS are

PFAS is a group of human-made chemicals. The Water Quality Association describes their widespread use since the 1940s in non-stick cookware, food packaging, stain and water repellants, and firefighting foams. That list explains why they show up in many places, including household products and, in some cases, drinking water.

They are known as "forever chemicals" because they resist degradation and can accumulate in the environment and in your body over time. That is one reason homeowners should pay attention to test results rather than assume their water is fine.

More recently, PFAS have been cited as a potential health risk, including increased risk of cancer, development effects in children and weakened immune systems. These potential health concerns do not tell you whether your water is a risk.

Three dates to know

Three dates anchor the rulemaking. Each one marks a different kind of step, and they are easy to mix up.

March 29, 2023: the proposal

On March 29, 2023, EPA proposed the first National Primary Drinking Water Regulation (NPDWR) for six PFAS. A proposal is a draft, not a rule. The April 2024 date below is the one that marks the final regulation. If a news story describes the March 2023 step as the rule taking effect, it is describing the proposal as if it were final.

April 10, 2024: the final rule

The Environmental Protection Agency announced its final National Primary Drinking Water Regulation for six PFAS chemicals on April 10, 2024.

May 14, 2025: intent to keep the 4 ppt levels

The third date concerns the numbers. The portal reports that EPA announced its intent on May 14, 2025, to keep the announced maximum contaminant levels (MCLs) for PFOA and PFOS at 4 ppt. The word that matters is intent. This was an announcement of EPA's plans, not the end of every question about the rule.

The 4 ppt limits

The two 4 ppt levels discussed here apply to PFOA and PFOS. The portal calls these maximum contaminant levels, or MCLs.

If you need the limit for a different chemical, look it up in EPA's rule text rather than relying on a summary, including this one.

Ppt is a very small unit. Labs report PFAS results this way, so you will see it on a test report. Check the unit before you compare a result to 4 ppt. If a report uses a different unit, ask the lab to restate the result in ppt before you compare it with the limit.

Who the numbers reach

The portal gives a national estimate: "It is estimated the drinking water supply for at least 19 million people in 43 states in the U.S. is contaminated with PFAS." That suggests a widespread concern, but it is still an estimate for the country as a whole. It cannot tell you what is in your tap, your well, or your neighbor's.

Keep the two separate in your head, and let your own water provider's results answer the local question.

Public water or a private well

Your first step depends on where your water comes from.

If you are on a public water system, start with the utility. Ask for its most recent PFAS results, the date they were collected, and where in the system the samples were taken. A result from the treatment plant describes water leaving the plant, and it may not describe water at the point where you use it. Ask the utility how it tests and how it reports results, so you know what a number on a future report will mean.

If you have a private well, ask about testing for your water supply. Ask a certified laboratory which PFAS it can measure and what reporting limit it uses. Ask your local or state health office whether it offers guidance or testing support for private wells in your area. A well test that does not include PFAS will not answer the question, so confirm the chemicals on the test list before you pay for it.

In both cases, keep a copy of every report. A dated record lets you compare results over time and gives a filter maker or a technician something concrete to work from.

Reading a water test report

A water test report is more useful when you read it in a fixed order. Start with the sample date, because a result from several years ago may not describe your water today. Next, check the location of the sample. Then look at the list of chemicals and the units. Only after those steps should you look at the result itself.

Pay attention to how the report presents a chemical it did not detect. A report may show a "not detected" entry alongside a reporting limit. That limit is the smallest amount the lab can measure reliably under its method, so a "not detected" entry means the result was below that limit, not that the chemical is absent. If the reporting limit is higher than 4 ppt, the report cannot show whether your water meets the 4 ppt level for PFOA or PFOS. Ask the lab about this before you draw a conclusion.

Finally, compare the numbers you can trust to the figures in this post. A report that does not include a chemical cannot give you an answer about that chemical.

Illustrative example: check a result before choosing treatment

Suppose a report lists PFOA at an illustrative 10 ppt. Confirm the sample date, location, units and reporting limit with the lab. Then bring the report to any discussion about treatment and match the chemical to the filter's certification listing.

If a result comes back above 4 ppt

A result above 4 ppt for PFOA or PFOS is worth acting on, but it is not a reason to panic, and it is not a reason to buy the first product you see. Start by confirming the result. Ask the lab to check the units, the sample date, and the reporting limit, and ask whether the sample was a single test or part of a series. A single result may be followed by more testing, and your utility or health office can tell you what its next steps are.

If the result came from a public water system, contact the utility in writing and ask what it plans to do, what the timeline is, and whether it will notify customers. Keep a copy of your correspondence. If the result came from a private well, ask your local or state health office what it recommends and whether it can help you find a qualified laboratory or technician for follow-up testing.

Only after you understand the result should you think about treatment. Bring the report, the chemicals it lists, and the units to any conversation about a filter. A product certified for those chemicals, as described below, is a better starting point than one chosen from an advertisement.

Filters: read the claim after the numbers

Filters are where advertising gets loudest, so it helps to know what a credible claim looks like. The portal describes EPA's guidance on certified filters for reducing PFAS in home drinking water and its reference to WQA certification listings.

A filter claim should point to something you can look up. "Certified" should mean a listing you can find and read, which names the product and the contaminants it is certified to reduce. A label that says a filter "removes PFAS" with no listing behind it is a marketing statement, not a certification. Ask the seller where the listing is, and then go look at it yourself rather than relying on the seller's summary.

Be careful with the difference between a filter that reduces a chemical and one that is certified for it. Reduction is a general word. Certification is a specific claim with a documented standard behind it. A product can reduce some PFAS and still not be certified for the ones in your test report. Match the chemicals on the listing against the chemicals in your results, not against the general word "PFAS."

Maintenance deserves the same scrutiny. Ask about the replacement schedule and the installation method. If a seller's claim depends on conditions you cannot check or cannot keep up with, treat the claim as incomplete until those conditions are written down and make sense for your home.

Before you buy

Before you spend money on a filter, write down answers to a few questions. If the seller cannot answer them in plain terms, that is useful information.

• Which PFAS does the certification listing cover? Start with the listing itself rather than the marketing page.
• Do the chemicals on the listing match the chemicals in your water test report?
• If your report includes PFOA or PFOS, what is the result in ppt, and how does it compare with the 4 ppt level?
• Where was the water tested: at the utility, at the treatment plant, or at your tap or well?
• What is the replacement schedule, and who handles it?
• What does the product claim beyond certification, and is that claim backed by a document you can read?

These questions help you compare a filter to the specific problem in your water, rather than to a general fear or promise. Use the home water treatment device checks to organize that review.

Check for later rule changes

For compliance deadlines, limits for other chemicals, state requirements or private-well guidance, go to EPA's own rule pages and to your state or local health and water agencies.

Before you make a decision that depends on the rule, check EPA's website for any later action, because a rule can change after the date on any summary, including this one.

Where to go next

Start with your own water today. Get the most recent PFAS results from your utility, or arrange a test if you have a private well, and confirm the units and the reporting limit. Then read the rule dates in this post, and check EPA's pages for current rule details. Only after that should you look at a filter, and when you do, judge the claim by the certification it points to and the chemicals it covers.

Questions to ask before you buy

Does a national estimate describe my tap water?

No, a national estimate cannot tell you what is in your tap water. Use results for your own water supply.

Does "not detected" mean a chemical is absent?

No, it means the result was below the lab's reporting limit. Check that limit before drawing a conclusion.

Does a general PFAS reduction claim establish certification?

No, check the product's certification listing for the specific chemicals in your water report.