How to Choose a Water Filter: Is it important to choose a filter that is certified? How to know which contaminants a filter removes and how much.

pitcher?  carbon block?  reverse osmosis? whole house? certified? nsf/ansi standards 42, 53, 58, 401?  


A survey by NSF International found 82% of Americans are concerned about the quality of their tap water. This survey predated the water crisis in Flint, Michigan.  Frankly, none of us knows what is in our tap water.  You want to remove contaminants from your water, but are not sure how to select a water filter.  It is quite simple. There are three key concepts:

  • NSF/ANSI water treatment standards;
  • Certification to those standards, and
  • Performance Data Sheets

If you do not want the detail I provide below, the bottom line is that you want a solid carbon block filter certified to NSF/ANSI 42, 53 and 401(and 58, if you would like to add reverse osmosis), and you must review the manufacturer's Performance Data Sheet to know which contaminants any particular filter reduces. Performance varies widely between filters carrying the same certification (read more below). My research led me to choose Multipure filters.  I use Multipure's Aquaversa model which is certified to Standards 42, 53 and 401.  Consumer Reports ranked Multipure's Aquaversa as its top under-the-sink water filter in the March 2017 issue. See Multipure's Performance Data Sheets here, including Aquaversa's.  Compare its cost, Performance Data Sheet and warranty to other filters you are considering.  By the way, Multipure's filters reduce the lead in water to safe levels, removing more than 99.3%. Note no certified reduction claim is valid when dealing with water as contaminated as Flint's, though.

When comparing the cost of water filters, also consider the number of replacement filters and the gallons of water each filter will process before needing to be replaced.  Frequent filter changes will get you in the long run.

After a lot of research, I chose Multipure filters. I offer them to you through this website, because they are the best I could find.  I offer what I use.  

If you have a question, please feel free to call me at (800) 294-1349 or email me I will not bother you with any follow up phone calls or emails or even try to sell you a water filter.  I simply share information.  I respect your privacy and busy life.  

In case you are interested in contaminants commonly found in tap and bottled water that are especially dangerous to pregnant women and young children, check them out here. Actually they are dangerous to us all.  

CERTIFICATION:  Consider only certified treatment systems or filters.  If certified, manufacturers are required to provide a Performance Data Sheet, listing contaminants reduced.  If a water filter or treatment system is not certified, you can only guess which contaminants it might reduce. Those manufacturers that choose certification will have the filter certified to the appropriate NSF/ANSI standard.  The three certifying organizations are NSF International, WQA (Water Quality Association) and UL (Underwriters Laboratories).  See more on certification below.

STANDARDS:  The standards to which water filters are certified are developed and published by NSF International and American National Standards Institute (NSF/ANSI). Four residential water treatment standards are described below. Water filters are certified to these standards. Certification (e.g., to NSF/ANSI Standard 53) means the filter has met at least some of the requirements described in that water filtration standard. "At least some" is a problem that is discussed below.  


NSF/ANSI 42: Drinking Water Treatment Units - Aesthetic Effects. Filters certified to this standard reduce specific aesthetic or non-health related contaminants (chlorine taste and odor and particulates).  These filters basically make your water more palatable.

Product examples:  The most common products certified only to this standard are water pitcher filters and refrigerator filters.

Multipure does not offer filters that are only certified to this standard.  

NSF/ANSI 53:  Drinking Water Treatment Units - Health Effects (also includes NSF/ANSI 42 certification).  Filters certified to this standard reduce specific health-related contaminants.These filters use carbon filtration. The quality of the carbon filter determines which contaminants are reduced and to what extent.  For that reason, filters certified to Standard 53 vary widely in their ability to remove contaminants.  You must consult a filter's Performance Data Sheet to learn which particular contaminants are reduced. Examples include Cryptosporidium, Giardia, some heavy metals (e.g., lead, pentavalent arsenic, mercury), pesticides, herbicides, benzene, MTBE, radon, trihalomethanes and PCBs.  It can be used in conjuction with reverse osmosis technology (certified under Standard 58) to remove additional contaminants.

Product examples: These filters are typically installed below the sink.  Some products may have two or three filters; others may have a single, more powerful solid carbon block filter. Some faucet-mount filters are certified to Standard 53, although they are unable to compete performance-wise with a larger solid carbon block filter.

Multipure's Aquaversa, Aquadome and Aquaperform filters are certified to NSF/ANSI 53. They are available for under-the-sink, countertop or inline use for a refrigerator.  See product descriptions here and Multipure Performance Data Sheets here

NSF/ANSI 401: Emerging Compounds/Incidental Contaminants.  This is a new standard that was developed in reaction to the public's concern over pharmaceuticals being found in our tap water.  Filters can be certified to reduce up to 15 contaminants, including over-the-counter and prescription drugs. Other contaminants included are new types of herbicides and pesticides, chemicals used as flame retardants and detergents. 

Product examples:  The most common product certified to this standard is a carbon filter that would be used under the sink, on the countertop or inline for a refrigerator.

Multipure's Aquaversa and Aquadome are certified to reduce all 15 contaminants. covered under NSF/ANSI Standard 401. They are available for under-the-sink, countertop or inline use for a refrigerator.  See product descriptions here and Multipure Performance Data Sheets here

NSF/ANSI 58: Reverse Osmosis Drinking Water Treatment Systems.  Certified reverse osmosis systems are able to reduce some of the same, but also entirely different contaminants than carbon filtration.  Likewise, carbon filters can reduce contaminants that a reverse osmosis system cannot. For that reason, reverse osmosis systems include carbon filters. Reverse osmosis systems are able remove perchlorate, fluoride, nitrate, nitrite, radium, and heavy metals such as hexavalent and trivalent chromium, cadmium, copper lead and mercury

Reverse osmosis systems should include pre-filters and a post-filter along with the reverse osmosis membrane.  The performance of this system is dependent upon the quality of the pre-filters and post-filter as well as the RO membrane.  Like carbon filters certified under Standard 53, RO systems vary widely in their ability to reduce contaminants.  You must consult the Performance Data Sheet. If the percentages of contaminants reduced are not listed, assume it is the minimum to pass certification.

Multipure's reverse osmosis, AquaRO, system uses three pre-filters.  Multipure's Aquaversa filter is used as the post-filter. See the product description here and Multipure Performance Data Sheets here


In my quest to understand what “certification” to a certain standard meant, I asked my public library if they could locate a copy of NSF/ANSI Standard 53.  It's not a very popular publication. They had to secure a copy from UCLA through an inter-library loan (it cost me $20 because it was out of state, but it was well worth it).  This standard, NSF/ANSI 53, goes into 118 pages of detail, including requirements for filter materials, structural performance, minimum performance requirements, elective performance claims and performance data sheet requirements. Many filters claim "NSF/ANSI 53" certification. All I wanted to know was what a filter certified to NSF/ANSI 53 removed and how much.  Unfortunately, that information was not provided in the standard itself.  It was at this point that I decided to call NSF.  By the way, NSF not only develops and publishes the residential water treatment standards along with ANSI, they also certify water filters.  I should add that there are two other organizations that certify products to the above standards – WQA (Water Quality Association) and UL (Underwriters Laboratories).


I spoke at length with a very knowledgeable and forthcoming NSF representative.  I would describe that conversation as “eye opening”.  It might be better classified as an “are you kidding me!” conversation.  This is what I learned:

If you select a water filtration system that is certified to one of the NSF/ANSI standards listed above, you will have the following assurances:

  • The system is structurally sound;
  • The system does not add anything harmful to the water;
  • Advertising, literature and labeling are not misleading;
  • The materials and production processes don’t change, giving you consistent product quality over time; 
  • Contaminant reduction claims made by the manufacturer are true. These claims are to be disclosed in a “Performance Data Sheet”.  

“Are you kidding me!” refers to the last bullet point.  Two different water filters can carry the same certification, from the same certifying organization (i.e., NSF, WQA or UL), yet be certified to reduce different contaminants and different amounts of those contaminants.  Please read the information I share below. You can’t properly select a water filter unless you know this information.  It may prevent you from buying a water filter that does not reduce the contaminants you thought it did. 




Again, what I learned from this NSF representative is you could have several filters that carried the same certification (NSF/ANSI 53, for example) with incredibly different performance. Their contaminant reduction claims could range from one contaminant to the most contaminants of any, at the highest percentages, of any filter on the market. I clarified my understanding with the NSF representative twice – a filter with one contaminant reduction claim could carry the same NSF/ANSI 53 (or other) certification as a filter that was certified to reduce the most contaminants of any on the market.  Yes, that is correct. Doesn't that make your jaw drop? No wonder so many people purchase the faucet-mount or water filter pitchers! They may have the same certification, but simply cannot compete with the larger, high-quality solid carbon block under-sink or countertop filters. See the five bullet points above.  Certification may only apply to the top four because the manufacturer may not have made any contaminant reduction claims.  Yet the best and the worst will have the same stamp on their product.






WHICH CONTAMINANTS DOES YOUR FILTER REDUCE AND HOW MUCH?   it’s all about the Performance Data Sheet!

The NSF representative did stress that if any contaminant reduction claims were made, the top four bullet points had also been met. Regarding the fifth bullet point above, manufacturer contaminant reduction claims, you must consult the manufacturer’s "Performance Data Sheet” to understand the contaminant reduction claims for any particular filter. The manufacturer is required to publish this information if a filter is certified.  Unfortunately, although the contaminants reduced are listed, the percent removed is not always provided.  There are minimum reduction requirements for each contaminant certified under an NSF/ANSI standard. However, a filter can be certified to remove a much higher percentage and even more contaminants than the minimum required under a given NSF/ANSI standard.  


As I searched for the filter that I wanted for myself, I found that Multipure’s Performance Data Sheets provided both the contaminants reduced and percentages of those contaminants that the filter is certified to remove. Multipure's filters were consistently the best I found.  I can't tell you how many filters/Performance Data Sheets I reviewed, but I spent hours comparing them on an Excel spreadsheet. I chose Multipure filters for my family. The choice was straight forward.

Click here to see Multipure's Performance Data Sheets for their solid carbon block filters, certified to NSF/ANSI 42, 53 and 401, and for the reverse osmosis system certified to NSF/ANSI 58.

I haven’t scoured the internet looking for this level of disclosure from other manufacturers, but I rarely ran across the level of detail Multipure provides.  If the percentages of contaminants removed are not listed, I assume it’s just the minimum amount required for certification.  If they are listed, compare them to Multipure filters. This is one of the many reasons I choose to use Multipure filters, and eventually decided to offer them to you and pass this information on to the most vulnerable of water consumers – pregnant women (and their fetuses), infants, children and those with fertility issues.


For over two decades, medical and environmental studies from across the globe have identified very common contaminants in our drinking water that put pregnant women and their fetuses, as well as infants and children at risk. Pregnancy risks include miscarriage, spontaneous abortion and stillbirth. Risks to children include birth defects, increased risk of childhood cancers, low birth weight and a range of cognitive disorders.

The rest of us face increased risks of cancer, liver, kidney or central nervous system problems, gastrointestinal illnesses and increased blood pressure, to name a few.

How do these contaminants make their way to the fetus? One avenue is through drinking water (tap and bottled), and pregnant women are instructed to drink plenty of it.  Let’s look at a landmark study which examined the umbilical cord blood of newborns.

In 2005 the Environmental Working Group (EWG) spearheaded a study to examine the umbilical cord blood of newborns.  Researchers at two major laboratories found an average of 200 industrial chemicals, pollutants and pesticides in the blood of these babies, born in August and September of 2004 in U.S. hospitals. These contaminants were passed from the mother to her fetus. Tests revealed a total of 287 chemicals in the group including pesticides, polychlorinated biphenyls (PCBs), perfluorinated chemicals (PFCs), mercury and wastes from burning coal, gasoline, and garbage. Contaminants in the water ingested by the mother are considered primary, contributing factors. EWG recommends that pregnant women filter their tap water.  

Of the 287 chemicals detected in umbilical cord blood, 180 are known to cause cancer in humans or animals, 217 are toxic to the brain and nervous system and 208 cause birth defects or abnormal development in animal tests. A follow up study on minority newborns was performed in 2009 with similar results.  Per EWG, “Had we tested for a broader array of chemicals, we would almost certainly have detected far more than 287”.


Review this website to learn more. If you think bottled water is your answer, please think again. Learn why here.  Do not rely on the water filter in your refrigerator, water pitchers with filters or those that attach to your faucet.  Commit to installing a solid carbon block water filter that is certified to reduce as much and as many of the contaminants that are finding their way into your homes and children.  I did the research and even called NSF International and the Water Quality Association, both of which certify water filters. I chose Multipure after much research and recommend their filters to your family without hesitation. Select your NSF certified Multipure filter here. See my tips on choosing one of those filters here. If you're concerned about installation, read my comments here.

Spread the word - This is important information, not only for pregnant women, but for all of us. The 287 contaminants found in the umbilical cord blood of newborns were from the mothers' bloodstreams. They're just as likely in yours and mine if we do not take measures such as installing a high-quality solid carbon block filter.  Adding reverse osmosis will remove additional contaminants.  As far as I can tell, the majority of physicians are not sharing this critical information with patients and it's not discussed in even the most popular pregnancy books.  Please share my website with friends, other pregnant women, and even your own OB-GYN and other medical professionals you see. Your child's pediatrician should be aware of this information as well. Again, if you purchase a Multipure water filter, you will know what you are getting.  You are choosing the best.