PFAS are a large family of manufactured chemicals used in consumer and industrial products, and they persist in the environment rather than breaking down. Massachusetts regulates six of them together, under a state standard called PFAS6, at 20 parts per trillion for the combined total in public water systems. Private wells are not covered by that standard — which is the part most homeowners do not realize, and the reason this page exists.
MassDEP set a state drinking water standard known as PFAS6. It is a combined limit of 20 parts per trillion for the total of six PFAS compounds taken together, rather than six separate limits. The six are PFOS, PFOA, PFHxS, PFNA, PFHpA, and PFDA. The standard is in effect.
MassDEP set that limit because of health concerns associated with these compounds, and the agency publishes its own reasoning and current guidance at mass.gov. That reasoning is the agency's to explain, not ours — we install plumbing, so we point people to the source for the health side of it rather than characterizing it ourselves.
Two things about the scope of the standard are worth being precise on. First, PFAS6 applies to public water systems — the towns and districts that deliver water and send a bill. Second, public water systems are required to report their PFAS results to their customers, which means the answer for a home on town water already exists and is free to go read. Your town water department has it, and so does the annual water quality report your system publishes.
Federal drinking water standards are set separately from the state standard, and they are their own subject. Check epa.gov for the current federal limits rather than relying on what any contractor site — this one included — says about them.
The state standard does not apply to your water. That is not a loophole — private wells simply sit outside the public water system framework, and the water quality is the responsibility of whoever owns the property. Nobody tests it on your behalf, nobody reports anything to you, and no result arrives unless you go get one.
MassDEP recommends that private well owners test for PFAS roughly every ten years. That testing requires an independent certified lab — PFAS is measured at parts per trillion, which is not something any field kit or on-site check can reach. The lab will tell you how to collect the sample properly, and that matters as much as the analysis.
Being straight about our own role here: PFAS testing is not something we perform, and it is not something we arrange. The certified lab is a direct relationship between you and them.
In Metrowest, this lands hardest on the well-heavy towns. Sherborn, Dover, Wayland, and Upton have a lot of houses on private wells, and every one of those households is in the go-find-out category rather than the read-the-report category. PFAS is one item on a longer list for a well owner — the rest of it is in our Metrowest private well guide.
Two approaches carry PFAS reduction claims, and both of them come with the same condition attached.
Now the condition, which is the single most useful thing on this page: certification under 53 and 58 is contaminant-specific. A filter certified under 53 for one contaminant is not certified for all of them. The standard number by itself tells you nothing — PFAS has to appear by name on that specific product listing. A cartridge certified for chlorine taste and a cartridge certified for PFAS can carry the same standard number and be entirely different products.
Two more things that come up constantly. A water softener does not remove PFAS. A softener removes calcium and magnesium hardness, and a great many homeowners believe that having one means their water is filtered. It does not. And the old standalone P473 protocol for PFAS was folded into 53 and 58 — it is not a separate certification to shop for anymore, so ignore advice telling you to look for it.
For a private well with a PFAS result, there are three general directions: point-of-use treatment at a single fixture, point-of-entry treatment for the whole house, or bottled water. Our answer is point-of-use reverse osmosis at the kitchen sink.
That means an under-sink system with its own dedicated drinking faucet on the countertop, optionally tied into the fridge line as well, so the water you drink and cook with is treated. We do not install whole-house reverse osmosis. The reason is simple: an RO membrane produces water slowly and sends part of it to drain, which suits a drinking tap and does not suit the volume and speed a whole house demands from its plumbing.
So the practical shape of it is that PFAS gets solved at the tap you drink from, not at the main. It is not a compromise so much as putting the treatment where the exposure that matters actually happens. The longer version of that reasoning is in our whole house filter vs. softener vs. reverse osmosis guide.
Water treatment gets sold on worry, so it is worth writing our own limits down plainly rather than letting them stay vague.
If a company offers to test your water for PFAS for free and then sells you the system that fixes what they found, that is worth thinking about for a minute.
If your water has been tested and you want an under-sink system plumbed in properly, call and tell us what the lab found. Mon–Sat 7am–5pm.