Choosing the Right Water Filter: The Importance of NSF Certification

When it comes to purchasing a new water filter it can be difficult to know what to look for, and often, it's a relief just to find a filter that fits your refrigerator or system. But in a world where you can often choose between 'original' or 'compatible' models, ensuring the filter you buy offers the same level of performance is really important. But how do we do that?

NSF Certification is the world leading standard when comparing water filters, and is often the key to finding a high quality filter with a guarantee that it will remove the contaminants it claims to.* This post will tell you everything you need to know about NSF Certification so that you can be safe in the knowledge that the next filter you buy is a high quality, 3rd-party tested product!

Who are NSF International?

NSF (National Sanitation Foundation) International is a not-for-profit organisation specialising in the testing, inspection and certification of sanitary products closely linked to public health. Founded in 1944 in Michigan, USA, NSF has been at the forefront of developing public health standards for almost 80 years, offering services within 180 countries and employing over 1200 people across the globe.

What is NSF Certification?

In essence, filters that bear the NSF Mark must meet the industry’s minimum performance guidelines. Whilst you may expect that from any filter you buy, sadly that is not always the case.

As per NSF, "the NSF mark is your assurance that a product has been tested by a trusted independent certification organisation. It is valued by consumers, manufacturers, retailers and regulatory agencies worldwide."

The testing process that is undertaken to receive an NSF certification is rigorous, testing over 60 parameters across material safety, structural integrity and contaminant removal claims. This also involves a full physical evaluation and inspection of the manufacturing facilities and processes for supply chain transparency.

The Important NSF Certifications for Water Filters

NSF certified filters come with the assurance of safety and quality. They are:

  • Made with BPA-free plastics, ensuring no harmful toxins seep into your water.

  • Constructed using robust materials for enhanced durability.

  • Certified through extensive third-party testing.

If you have particular concerns about contaminants in your water, NSF certifications can offer you the peace of mind that the filter you purchase is tested and certified to remove the contaminants in question.

To be clear, there is not just one NSF certification but several that cover various different types of contaminants. Below are the most important standards for customers to be aware of when it comes to water filtration.

NSF 42 - Aesthetic Effects

Filters holding the NSF 42 certification have demonstrated that they are effective at eliminating 'aesthetic' related contaminants i.e. chlorine, taste and odours. Other contaminants that can be covered by this certification include iron, manganese, zinc, and total dissolved solids.

The majority of filters with this standard have been tested for reduction of chlorine, taste and odours which is often seen as the minimum requirements of any filter. Premium filters combine this with other standards shown below:

NSF 53 - Health Effecting Contaminants

NSF 53 certification is given to activated carbon filters that effectively reduce common but harmful contaminants such as:

  • Lead

  • Volatile Organic Compounds (VOCs)

  • Methyl Tertiary Butyl Ether (MTBE)

  • Cysts like Giardia and Cryptosporidium

However, it's important to note that these filters are not designed to eliminate highly dangerous substances like pesticides and nuclear byproducts.

NSF 58 - Membrane Filters and Dangerous Contaminants

Filters with NSF 58 certification use advanced membrane technologies, including reverse osmosis or nanofiltration, to remove severe contaminants such as lead, pesticides, and nuclear byproducts.

More can be found here with the NSF/ANSI 58 Technical Requirements.

NSF 401 - Emerging Compounds and Incidental Contaminants

NSF 401 is a newer certification, typically relevant for carbon and RO water systems. It focuses on 15 critical contaminants, including herbicides, pesticides, pharmaceuticals, BPAs, and other pollutants from agricultural and industrial sources.

How to Choose the Right NSF Certified Water Filter

Now that we know what NSF certifications are, we can look at the factors we need to consider when choosing the right filter. It's important to note that NSF certification does indicate a high quality product but doesn't always mean the best value for money!

Here are the main things to consider:

  1. What filters are compatible with my refrigerator or system?

  2. What NSF certifications does it have?

  3. What contaminants am I most concerned about?

  4. What is the rated capacity?

  5. Price

Before reviewing filters, the first thing you should confirm is what filters are compatible with your particular refrigerator or system. This will narrow down your options significantly.

You then want to consider what NSF certifications each filter has. If you are able to, we would always recommend looking for an NSF 53 and NSF 401 certified filter, as this has been further tested to remove another range of contaminants that can have negative health impacts. The more contaminants removed, the better as this will provide the most benefit to you and your family's health.

You also want to consider the capacity of the filter before looking at the price, as this will allow you to accurately gauge value for money. If the filter has a very low capacity but is equally priced with a filter that has a high capacity, then it's clearly not going to be as cost effective.

Genuine branded filters such as those by Samsung, tend to have the highest levels of NSF certifications including NSF 42, 53 and 401, whereas some compatible models will only have NSF 42. For this reason, you cannot just base your purchasing decision on price as often, the cheaper filter may be far inferior.


We hope this guide gives you all the information you need to go out and find the best filter for your needs. To summarise, NSF certifications are an important quality standard when comparing filters and provide a clear and trusted way of confirming the quality and effectiveness of your water filter.

There are various NSF standards that are relevant to water filters including NSF 42, 53, 58 and 401, however NSF 42 is the most common, covering chlorine taste and odours. When it comes to purchasing a filter, it's important to look for the NSF standards that the filter has been tested against as this is the clearest way to verify whether the filter is effective at removing contaminants.

When comparing filters, you must always bear in mind that cheaper filters may not have any NSF certifications at all or the most standard NSF 42, whereas others that are more expensive have more certifications and therefore offer the most benefit in terms of contaminants reduction.

NSF is a great way to compare filters but as with all things, it comes down to personal choice on what provides the most cost-effective benefits, but we always recommend to go with the best quality filter you can find!

Additional Resources

NSF Certification Database

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