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One of the main things to consider when purchasing a drinking water filtration system is the contaminants it will remove. There are literally thousands of water filters (some with fairly elaborate claims) on the market today made by hundreds of companies. A company can say anything in its literature or on its web site, and how can you evaluate the claims to determine if they are true - do you believe the company's lab reports, the glowing testimonials on their web site, the celebrity endorsements? The information may be accurate, but HOW CAN YOU KNOW?
Certification by an independent third party like NSF International is the best way of identifying those water filters that some group (besides the manufacturer) has reviewed and determined to perform as advertised. There are two ANSI/NSF standards that pertain to drinking water filtration systems: Standard 42 for Aesthetics Effects (cosmetic factors like taste, odor, chlorine, and particulate reduction) and Standard 53 for Health Effects (the contaminants that are harmful to health).
For example, below are three contaminant reduction lists from NSF
International. They are 3 of the 12
companies listed when ‘MTBE reduction’ was checked on the search engine
at the NSF International site under the category “Reduction Claims
for Drinking Water Treatment Units - Health Effects”
This list illustrates the way some companies “play the certification game” by 'padding the list' to make their contaminant list appear longer than other companies. They pay separately to have individual Volatile Organic Compounds (VOCs) tested, certified and listed. However, if the filter is certified for VOC Reduction, all of the individual VOCs on the NSF table below are already significantly reduced and do not need to be re-certified and re-listed - except to try and impress their potential customers.
In the lists below:
Contaminants that are NOT VOCs in the reduction list are identified in Highlighted Text
Certification for VOC reduction is indicated by VOC Reduction
Specific VOCs that have been separately (and redundantly) certified for reduction are indicated by VOC-
Contaminants listed under ANSI/NSF Standard 53 for Health Effects on the NSF International web site:
8 different contaminants
9 different contaminants
Multi-Pure 880 series
10 different contaminants
The specific VOCs that have been separately certified in the lists above have been highlighted.
Other important considerations when evaluating and selecting a water filtration system that you plan to use for many years include:
Pore size of the filter media - smaller is better. Smaller particulates
are removed, and water comes into contact with more of the filter media (the
Solid Block Activated Carbon (SBAC) or Granular Activated Carbon (GAC). SBAC is more effective for a given size of filter cartridge and at a given flow rate than a GAC filter. GAC filters also have large pores that let more contaminants pass through, because all of the water may not contact the filter media.
Physical size and capacity. All other things being equal, a larger filter will be more effective removing contaminants at a given flow rate than a smaller filter. Filter effectiveness depends on the water's contact time with the filter media - a larger filter allows the water to have more contact time. Smaller filters must also be changed more frequently than large filters, and they do not do as good a job during their rated life.
Long term cost of replacing the filter cartridges. Some of the smaller filters may be less expensive initially than a large filter, but when several years of filter replacement are considered, the larger filtration system may be more economical.
Construction materials of the filter housing. Some filters are light weight plastic that will need to be replaced every few years. Other filters are heavy gauge stainless steel and will last a life-time.
Warranty and the length of time the company has been in the water filter business. If you do invest in a more expensive, high-end filtration system, you want some assurance that when you want to replace the filter cartridge over the next 20 - 40 years the company will still be in business. There are no absolute guarantees, of course, but a company that has already been in business for many years at least has a track record for reliability.