It’s boom time for water filters, since Notified by EPA that as many as 10 percent of US water systems may have unsafe levels of PFASalso known as “permanent chemicals,” in water. The lead pipes are still there all over the placeeven if they are out of Flint, Michigan, in July 2025. Heck, there probably is heavy metals in groundwaterdepending on where you are, and Bottled water is dangerous with too much microplastics.

I’m not saying this to make you panic. Your drinking water likely meets federal standards, and only about 4 percent of water systems have unsafe levels of contamination, according to an EPA study in 2020. According to this, local water systems not required to comply with new federal PFAS and PFOA maximums for drinking water until 2031.

In response to concerns about the water supply, a new generation of water filters is making amazing promises about reducing pollutants: chlorine, PFAS, heavy metals, stray pharmaceuticals like acetaminophen, fluoride if that’s a concern for you. Some of these are whole-house 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 trustworthy? It’s me test water filters since 2024, always uses chemical indicators and equipment, and can prove that it is not always easy. Here’s a quick guide to checking that water filter that caught your eye.

What are the NSF/ANSI Water Filter Standards?

The first main source of comfort for me in assessing water filters is certifications and independent testing. Vague claims of 99 percent reduction in chlorine or PFAS or arsenic are harder to trust when the testing is internal to the company itself. To be reliable, any third-party test claim must also clearly identify the lab that performed the test.

The most reliable, standardized form of certification is testing against NSF/ANSI standards. NSF, formerly the National Sanitation Foundation, is a Michigan-based, non-governmental nonprofit founded in 1944 that develops and certifies compliance with a number of different test standards—including those for water filters. ANSI, or the American National Standards Institute, is an independent nonprofit that accredits accreditation and testing organizations such as NSF.

there three main NSF / ANSI standards which can be used in filters for domestic drinking water.

• NSF-ANSI 42: Drinking Water Units—Aesthetic Effects.
  This confirms the removal of substances that are not considered harmful but may affect the cosmetics or taste of the water. This includes chlorine and chloramine used in cities to disinfect drinking water.
• NSF/ANSI 53: Drinking Water Units—Health Effects
  It verifies the removal of any number of compounds thought to be harmful, including lead, arsenic, PFAS, and more. Each compound is tested individually, among more than 50 possible contaminants.
• NSF/ANSI 401: Emerging Compounds/Incidental Contaminants
  This confirms the filtering of compounds that “emerge” as potential concerns, including drugs, herbicides, and pesticides.

If you have the item, it can be marked in the box. But don’t think that certification is the norm. our shower water filters in particularonly one filter has received certification from the NSF for free chlorine removal: the Weddell Duo.