Home water filter with clear water on windowsill

Not surprisingly, we spend a lot of our time reviewing water filters. So when it comes to making sure products are able to remove unwanted contaminants from your tap supply, we know what to look for.

With Amazon often finding itself in the spotlight for selling subpar or counterfeit goods on its marketplace, we decided to find out exactly how many of the water filtration products listed by the retail giant can back up their claims with genuine filtering certifications.

We looked into over 550 of Amazon’s top water filter products, cross-referencing them with NSF international’s Certified Product and Service Listings. The results? Well, let’s just say that we’re going to be reading Amazon product descriptions pretty closely from now on.

Here are the findings from our research, plus some key pieces of information on water filter certifications, and how to source legit filtration products.

What did we find when we reviewed Amazon’s water filters?

Key findings

  • Of the top 590 filter products listed on the Amazon.com marketplace in October 2020, only 102 cited a relevant NSF/ANSI standard that matched their filtering claims.

  • An additional 66 filters did possess NSF/ANSI certification in some form. However, a general certification doesn’t guarantee that a filter has been tested and approved for its intended purpose.

  • 71.5 percent of Amazon’s top listed filters have no NSF/ANSI certification whatsoever. While it’s important to say that some brands are selective about which products they submit for NSF testing (Brita being the most famous example), this leaves consumers without a way to independently verify the credentials of many top-selling filtration products

Full results

Here are the full results of our survey, split into the major filter types—pitcher and countertop filters, reverse osmosis filters, refrigerator and MWF filters, under-sink filters, portable filters, well water filtrations systems, and water softeners.

Understanding the results

Who is the NSF?

NSF International is a major globally recognized independent organization that sets standards for safe and effective consumer goods, especially those involving food and water processing. They also test and certify products according to their own standards.

NSF develops their standards in collaboration with national arbitrators such as the Environmental Protection Agency (EPA) and are accepted by the American National Standards Institute (ANSI).

When it comes to home and commercial water filters, NSF has led the development of the American National Standards (ANS) since the 1970s. While manufacturers aren’t legally required to submit their products for NSF evaluation, those that do are subjected to rigorous testing in their Michigan-based labs.

Aside from the NSF, there are other reputable water testing boards, including The International Organization for Standardization based in Switzerland. All major testing or certification bodies, including the ANSI, WQA, and the CAN in Canada, certify products against NSF codes.

NSF/ANSI standards

Here’s a quick reference table on what the NSF/ANSI standards mean:

NSF/ANSI certification Frequently tested devices What do these filters remove?
42, 53 Pitcher, faucet, refrigerator, and
other activated carbon filters
  • Organic contaminants
  • Chlorination byproducts
  • Cleaning solvents, pesticides
  • Cryptosporidium
  • Lead
58 Reverse osmosis (RO) filters
  • Most bacteria and viruses
  • Nitrates
  • Sodium
  • Dissolved inorganics
  • organic compounds
  • Pesticides and petrochemicals
55, 244 Ultraviolet (UV) filters
  • Bacteria
  • Viruses
NSF/ANSI standards quick reference table

How to spot an uncertified water filter

Here are our top five tips to ensure you’re purchasing a water filter that will genuinely improve the taste of your tap supply and protect from possible pollutants:

The takeaway?

Until Amazon is held more accountable for the quality of the products on their marketplace, there will always be an added risk factor when shopping on their site. If that means receiving the wrong type of shampoo or a counterfeit t-shirt, you might feel pretty annoyed. But the consequences of misleading filtration products, which can mean the difference between drinking safe and potentially hazardous water, are much more serious.

As is the case with many elements of our national infrastructure, there’s growing skepticism over the quality of water produced by public treatment works. Thanks to increasing demand, spending cuts, and the effects of climate change, water sources are quickly degrading in some states. Meanwhile, advocacy groups and charities are claiming that EPA limits on acceptable contaminants are nowhere near stringent enough to produce a healthy drinking supply—all of which adds to the idea that filtering tap water may soon be seen as a necessity instead of a luxury.