You’ve probably heard that you should only choose water filters certified by the NSF. But what does that mean? Who is the NSF and why should we be listening to them? And what do all these numbers mean?
Let’s try and make sense of it all, shall we?
NSF International is an organization that certifies basically anything that could be used for food or beverages. NSF tests and retests these products to see if they meet their criteria for blocking specific contaminants in a lab setting.
To keep their certifications from becoming meaningless, the NSF spends a lot of time and a lot of effort making sure that they do not make mistakes. So the NSF certifies one specific product, for specific contaminants, from one specific company.
This process of certification costs a lot of money, and takes a lot of time. And this is where the first layer of confusion starts.
Let’s imagine that 3M makes a product called the UltraPure. They pay the NSF to prove that this product can remove the taste and smell of chlorine, which is NSF 42. They also pay the NSF to verify that this product can remove lead, which is NSF 53. This UltraPure can now get the shiny gold sticker that says “meets NSF 42 and 53 standards”.
But what if another company made an arrangement with 3M. In this arrangement, this new company would have 3M make the exact same product, but add their own label and package. And they want to call this product the Glacier Fresh.
This Glacier Fresh product cannot legally claim that it has NSF certifications. Even if the product is identical.
And why the difference?
3M applied for certification. They used their box and instructions. They paid for the tests they wanted. And NSF ties the certification to the exact brand and model name submitted.
Okay, okay, so the same exact product can have different certifications, based on the company that paid for them. But that should mean we can just use the NSF certification codes, right? Unfortunately, not so fast.
Let’s say you want to remove lead and toluene, because they showed up in your water test. The NSF code for both of those is 53. But the trick is that NSF 53 isn't a blanket approval. A filter certified for lead under NSF 53 isn't automatically certified for toluene.
And unfortunately, there are also some areas of ambiguity. Take THMs, or trihalomethanes. These are chlorination byproducts and are generally considered a cosmetic issue. That is, it’s not harmful, it’s just icky. Activated carbon is the go to solution for cosmetic issues and has been for decades. But to keep costs down, even if the filter could pass the test, some manufacturers choose not to get the NSF certification for trihalomethanes.
Now industry professionals know this, and the workaround is pretty simple. Focus on the contaminants that could actively harm people. Filtering those out should also, as a side effect, handle the cosmetic issues. But this is not common knowledge and adds to the confusion.
And that’s why many brands invent alternatives to the NSF. Not because they’ve reinvented the wheel but because they can’t be bothered to meet NSF’s exacting standards and regulations. And they can point to using activated carbon for cosmetic reasons as the excuse for not getting every last single NSF certification that they could get.
And, like a lot of things, this gets even worse on social media. Influencers will repeat marketing claims because they want you to buy the thing so they can get their referral payoff. You’ll see plenty of filters with the right buzzwords but no proof. There will be viral trends that will sell you unverified junk and, once you spend the money, you’ll work twice as hard to convince yourself you didn’t make a mistake.
While the NSF stands apart with an independent, public database, with regular factory checks, and clear rules, all of that fails in the face of professional marketing and influencer hype.
So what the hell are we supposed to do?
Well, first, I highly recommend a good, hard scream. Then, a deep breath or two.
And then the following steps.
Step 1: Test Your Water.
Use a real lab so you can know what's in your tap. I suggest National Testing Labs or TapScore
Step 2: Check the NSF
If you go to the NSF Listing and check the exact contaminant list under each standard, you should be able to match this list, point by point, to your water test results. Then, when you hit search…
Step 3: You’ll find the filters that match.
And now you’ve got a short list of filters that will absolutely work for the contaminants in your water.
NSF certification is the most reliable benchmark we have, but it's not simple. Identical filters carry different badges. Fake certifications are polluting the market. And there are a million different ways to be misled.
But just remember: start with a water test, then hunt down the exact NSF filter you need and doubt anything that isn't NSF-listed. This is how you find a filter that actually works for you and your water. This is how you find The Right Filter.
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