Three filter types that reduce PFAS
EPA names three home technologies that can reduce PFAS. Each works a different way, and each needs the right certification to count.
- Reverse osmosis (RO): Water is pushed through a very thin membrane that holds PFAS back. It is the most reliable home option, including for shorter-chain PFAS that carbon handles less well.
- Activated carbon: PFAS stick to the carbon as water flows through. A certified carbon block works well for PFOA and PFOS, as long as you replace it on time.
- Ion exchange resin: Small beads attract and hold PFAS. PFAS-selective anion resin is a strong option, especially paired with carbon.
If you want one answer, an under-sink RO system certified for PFOA and PFOS covers the widest range. A certified carbon filter is a reasonable, lower-cost choice when PFOA and PFOS are your main concern.
Chain length matters. PFOA and PFOS are long-chain PFAS, which carbon grabs well. Short-chain types, like PFBS and PFBA, slip through carbon sooner. RO and specialty resin hold onto them better.
Most under-sink RO systems also include carbon stages before and after the membrane. That gives you two barriers in one unit.
The certification to look for
Look for a product certified to NSF/ANSI 53 (carbon and resin filters) or NSF/ANSI 58 (reverse osmosis). The listing should name PFOA reduction and PFOS reduction specifically. A general NSF mark for chlorine or taste does not cover PFAS.
NSF used to certify PFAS filters under a separate protocol, P473. Those claims now live inside Standards 53 and 58, so you may still see the old name on older packaging.
Know what the claim proves. Certified filters are tested to bring combined PFOA and PFOS below 20 parts per trillion (ppt). That test was set before EPA's 4.0 ppt limits. EPA and NSF say the standards are being updated, but certification does not yet confirm a filter reaches the new federal levels.
Five accredited bodies certify these filters: CSA Group, IAPMO R&T, NSF, UL and WQA. Each keeps an online directory where you can check the exact model. For more on reading a listing, see what NSF certified means.
What does not remove PFAS
- Water softeners: Minnesota Department of Health sampling found whole-house softeners do not remove PFAS. The same goes for iron filters.
- Boiling: Boiling does not remove PFAS.
- Uncertified carbon filters: Performance varies widely. Without a PFOA/PFOS claim, you can't know what a filter does.
- Overdue cartridges: A spent carbon or resin filter can stop working without warning. EPA notes that replacing a filter late can increase your PFAS exposure.
| Process | PFOA and PFOS | Short-chain PFAS | Certification to look for |
|---|---|---|---|
| Reverse osmosis | Best | Best | NSF/ANSI 58, PFOA/PFOS reduction claim |
| Carbon block | Good, if replaced on time | Partial; breaks through sooner | NSF/ANSI 53, PFOA/PFOS reduction claim |
| PFAS-selective anion resin | Good | Good | NSF/ANSI 53, PFOA/PFOS reduction claim |
| Water softener | Not effective | Not effective | None for PFAS |
| Boiling | Not effective | Not effective | None |
Kitchen tap or whole house?
Most homes treat PFAS at one tap. A point-of-use (POU) system treats the water you drink and cook with, usually at the kitchen sink. A point-of-entry (POE) system treats all water entering the house.
Minnesota health officials note that POU units are more economical than POE units. They also say RO is more practical at a single tap than for a whole house. Whole-house carbon or resin systems exist, but they cost more to buy and maintain.
A good middle ground is a certified POU filter at the kitchen sink and refrigerator line. If you are also weighing whole-house treatment for other reasons, read whether a whole-house filter is worth it.
Check your water before you buy
EPA advises checking whether your water has been tested for PFAS first. A filter may not be useful if PFAS were not detected, or are below federal limits.
- City water: Check your utility's annual water quality report (Consumer Confidence Report), or call and ask about PFAS results.
- Private well: Use a certified lab that tests for PFAS. Your state health department can point you to one.
For context, EPA's final limits for PFOA and PFOS are 4.0 ppt each. In May 2026, EPA proposed giving water systems until 2031 to comply. It also proposed rescinding limits for PFHxS, PFNA, GenX and a mixture hazard index. Those changes are proposals, not final rules.
Keep it working
Every PFAS filter needs maintenance to keep its rating. Follow the manufacturer's schedule and use approved replacement cartridges.
Penn State Extension lists typical intervals. Pitcher cartridges often last about 2 months. Under-sink carbon filters run about 6 to 12 months. RO membranes usually last 12 to 24 months. Set a reminder when you install a new cartridge. Our guide on how often to change a water filter covers the details.
RO has a few extra needs. It takes space under the sink and a drain connection. It also sends some water down the drain as it works. See how much water RO wastes before you choose.