Wednesday, May 25, 2016

Demystifying NSF/ANSI standards for water filters (part 1)

In a couple of previous posts, Do we really need water filters 2, Evaluating the necessity and usefulness of water filters for domestic tap water and Why the Sawyer mini filter is my current favourite portable water filter, I touched on the NSF/ANSI (National Sanitary Foundation International/ American National Standards Institute) standards, specifically standard 42 and 53. I thought that more information about these standards should be addressed and at the same time provide an update on other relevant and newer standards.

Do you know that NSF/ANSI standards actually cover many diverse activities seemingly related only by their effects on health? They range from food equipment to vending machines, dietary supplements and residential dishwashers, making up to about 50 standards. But for the sake of the topic in this blog, I shall just present the following ones relevant to water filtration/purification.

Technically, all the following have the prefix "NSF/ANSI standard"
  1. 42: drinking water treatment units - aesthetic effects
  2. 44: residential cation exchange water softeners
  3. 53: drinking water treatment units - health effects
  4. 55: ultraviolet (UV) microbiological water treatment systems
  5. 58: reverse osmosis (RO) drinking water treatment systems
  6. 60: drinking water treatment chemicals - health effects
  7. 61: drinking water system components - health effects
  8. 62: drinking water distillation systems
  9. 177: shower filtration systems - aesthetic effects
  10. 401: Treatment Systems for Emerging Contaminants
  • Standards 44 and 177 are rarely applied in this part of the world (Singapore) since we hardly use water softeners and shower filtration. But they see significant usage in places like USA. (Updated by author: I am referring to residential usage. In commercial, industrial and academic setting, water softening is of course used. E.g. to get consistently good tasting coffee in Starbucks, you need to soften the water to a consistently low level of calcium and magnesium.)
  • Standard 401 is newly developed in reaction to the public's concern over pharmaceuticals in drinking water.  This standard covers up to 15 contaminants including drugs, herbicides, pesticides, chemicals used as flame retardants and detergents.
  • Of the greatest interest to most consumers will be the ones I have made bold - standards 42 and 53.

If the above list looks formidable (actually only 10 out of the 50 standards), don't worry. I am not going through all of them.

In a next post, I will use NSF/ANSI 42 as an example to illustrate how the standards can be applied to your water filtration situation. Once you get the hang of these standards, you can go ahead to find out about the rest yourself or you can wait for my future posts. (Besides 42, I recommend looking at 53 at least plus 58 if you have/want a RO system or 62 if you have/want a distillation system.) But for a start, let's go through some basics.


Read this first... some background information
  1. If you try to search for the document online, good luck! It is apparently not available in digital format (yet), even on the official NSF website -
  2. Hardcopies are hard to come by too. You probably have to order 1 from NSF itself. Luckily for me, my campus library has a few standards on hardcopy.
  3. If you do manage to find a hardcopy of the standard, reading through is not exactly a walk in the park. You have to wade through legal talk and technical jargon. And in the end, you may still not find what you want.

All right, do I really need NSF/ANSI certification?

Probably the most important question.

But since I am not you, I don't know about your situation - water quality, budget, constraints etc. So I will answer this from my perspective.
  1. NSF/ANSI happens to be a prevalent certification, if any, for water treatment units in the market. Therefore, YES! I prefer to get a water filter certified under NSF/ANSI (especially standards 42 and 53) but please note that a standard itself is not as straightforward as you think. There are some finer details you HAVE TO CONSIDER.
  2. However, note that these standards have so far been used to certify residential units. Certified portable units are still few and far between but there seems to be trend in this direction too.
  3. There are of course other certifications and endorsements out there e.g.
    1. US EPA (Environmental Protection Agency)
      caters more for removal of microbes by portable units in the outdoors
    2. Red Cross, Red Crescent, Unicef
      Some filter suppliers will quote that various Red Cross, Red Crescent chapters, Unicef etc. have approved the use of their filters in various humanitarian relief situations
    3. Some countries e.g. Japan have their own certification schemes
    4. The above are all fine, I suppose but do ponder on whether the above situations apply to you. Are you living in a refugee camp with an inadequate and unreliable supply of water?
If you decide you want NSF/ANSI certification for your filter, check that
  1. It is clearly stated on your filter's packaging and documentation that is certified as such.
  2. Double check that your particular brand/model really does come with the certification. This is the easy part, simply go to:
      This can search for filters according to manufacturer, brand, model, standard, claim and others
    2. For example, if you want to check for NSF/ANSI 42 certification, simply choose the standard from the drop-down list, and click "Search". You should find your desired filter inside the results, it really is what it claims it is.

As mentioned earlier, being certified under a standard by itself is not enough, you have to look deeper to check if you are really getting what you want. I will cover this in a next post...

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