It’s boom time for water filters, ever since the EPA announced that as many as 10 percent of US water systems may have unsafe levels of PFAS, also known as “forever chemicals,” in the water. Lead pipes are still all over the place, even if they’re no longer in Flint, Michigan, as of July 2025. Heck, there are maybe heavy metals in the groundwater, depending where you are, and bottled water risks excess microplastics.
I don’t say this to panic you. Your drinking water is probably in compliance with federal standards, and only around 4 percent of water systems end up with unsafe contaminant levels, according to an EPA study in 2020. This said, local water systems won’t have to comply with the new federal PFAS and PFOA maximums for drinking water until 2031.
In response to worries about the water supply, a whole new generation of water filters are making wondrous promises about reductions in contaminants: chlorine, PFAS, heavy metals, stray pharmaceuticals like acetaminophen, fluoride if that’s a worry for you. Some of these are whole-home or under-sink reverse osmosis systems. Others are simple countertop systems, gravity-fed through mesh or carbon or other filters.
So how do you sort out which water claims are credible? I’ve been testing water filters since 2024, often using chemical indicators and equipment, and can attest that it isn’t always easy. Here’s a quick guide to checking up on that water filter that caught your eye.
What Are NSF/ANSI Water Filter Standards?
The first main sources of comfort for me when assessing water filters are certifications and independent testing. Vague claims of 99 percent reduction in chlorine or PFAS or arsenic are harder to trust if the testing is internal to the company itself. To be credible, any claims of third-party testing should also clearly identify the lab that conducted the testing.
The most reliable, standardized form of certification is testing against NSF/ANSI standards. The NSF, formerly called the National Sanitation Foundation, is a Michigan-based, nongovernmental nonprofit founded in 1944 that develops and verifies adherence to a number of different testing standards—including those for water filters. ANSI, or the American National Standards Institute, is an independent nonprofit that accredits accreditation and testing organizations like the NSF.
There are three main NSF/ANSI standards that apply to filters for home drinking water.
- NSF-ANSI 42: Drinking Water Treatment Units—Aesthetic Effects. This certifies removal of substances that aren’t considered harmful but may affect cosmetics or taste of the water. This includes the chlorine and chloramine used by cities to disinfect drinking water.
- NSF/ANSI 53: Drinking Water Treatment Units—Health Effects This certifies removal of any number of compounds thought to be harmful, including lead, arsenic, PFAS, and others. Each compound is tested individually, among more than 50 possible contaminants.
- NSF/ANSI 401: Emerging Compounds/Incidental Contaminants This certifies filtering of compounds that are “emerging” as potential concerns, including pharmaceuticals, herbicides, and pesticides.
If you have the item in hand, these may be marked on the box. But don’t assume certification is the norm. Among shower water filters in particular, only one filter received certification from NSF for free chlorine removal: the Weddell Duo.
How to Verify Independent Lab Testing of Water Filters
There are three main lab bodies accredited by ANSI to test to NSF/ANSI standards. NSF provides its own certifications, of course. But two other entities are also able to certify adherence to NSF/ANSI: The Water Quality Association (WQA) and IAPMO (The International Association of Plumbing and Mechanical Officials).
In practice, you’ll have to check all three organization websites to verify whether a filter has been certified. The tests conducted by all three labs must adhere to the same protocols and standards, and include not just initial testing but continual audits and recertification. Here’s how to look up individual products.
- The NSF has a product search that allows you to look up products by name, to see whether they’ve been certified by the NSF. Here’s the link for NSF-certified drinking water filtration systems.
- The Water Quality Association (WQA) is a water treatment industry group that bills its WQA Gold Seal as the “oldest third-party testing and certification program in the water treatment industry.” The WQA website’s product search allows you to search by product name, product type, and the contaminant that has youmost worried.
- IAPMO (The International Association of Plumbing and Mechanical Officials) is a century-old organization with an ANSI-certified lab called IAPMO R&T. This lab also newly offers certification to NSF standards. You can search for IAPMO R&T certification at this product search site, by typing in the name of the company and searching under “Listee Name.”
Because certification is a lengthy and expensive process, requiring investigation into each filtered substance in order to receive certification, water filter companies often also cite other independent testing showing filter efficacy—but not all of this testing is backed up by a certification.
A Case Study
For example, here’s a water pitcher I’ve been testing from Clearly Filtered. It’s one of a newer generation of gravity-fed water pitchers that promise much more ambitious filtration than the classic fridge filters of yore. The Clearly Filtered pitcher promises near-total removal of up to 365 contaminants ranging from PFAS to ammonia to basic sulfites, while leaving helpful minerals like calcium and magnesium intact.
To check credibility, the first thing I’ll do is click into the brand’s performance results page, to see the source of those claims. In this case, it’s testing by an independent lab, a division of IAPMO called QFT, which itself has been certified as an international testing laboratory capable of testing to NSF/ANSI standards. So far so good. That said, tests were conducted in 2021, which means some testing protocols may have changed in the meantime. This is acknowledged in a disclaimer on the site.
Next up, certifications. Clearly does not show up as certified by IAPMO, but it is certified by the other two. (Most devices only maintain one certification, so it’s actually a little unusual to see a pitcher pop up certified by multiple testing labs.) Clearly Filtered’s water pitcher is certified to NSF standards for chlorine removal, and separately for lack of lead in its manufacturing processes.
I happen to know that Clearly Filtered was also among the first of its kind to be certified for PFAS and PFOA removal by the WQA, according to NSF/ANSI standard 53. But as of February 2026, this certification doesn’t turn up.
It turns out that Clearly Filtered is in the process of transferring its certifications from WQA to NSF. And so the filter maker is reapplying for PFAS-filtering certification under newly revised standards by NSF. If and when this happens, Clearly’s pitcher would be the only water pitcher filter certified by the NSF for PFAS removal.
This happens to be a filter I already know and recommend. But it does serve to demonstrate that verifying certifications can be quite complex.
In still other cases, looking up certifications can be even more perplexing: Brita certified two models of pitcher that use its Brita Elite filter—the Typhoon and the Pacifica—for lead removal with the NSF. But other models like the Denali ($31), which use the same filter, are not certified on the NSF website, but are instead certified by the WQA.
One last clue is looking at the type of filter being used. For PFAS in particular, the EPA recommends looking for filters that advertise granular activated carbon filters, ion exchange resin filters, or reverse osmosis as their filtration methods.
Power up with unlimited access to WIRED. Get best-in-class reporting and exclusive subscriber content that’s too important to ignore. Subscribe Today.
The post Which Water Filter Pitchers Filter PFAS? How to Check appeared first on Wired.
