Fluoride Action Network

Considerations When Buying a Water Filter

Fluoride Action Network | August 2012

FAN does not endorse any specific water filter, nor any other kind of product. Nor are we experts in the differences among the various filtration systems that are currently on the market. We offer, however, the following comments to help assist those who are seeking to purchase a water filtration system.

1) Effectiveness of Reverse Osmosis Can Vary Based on Flow Rate

Wehave learned from Dr. Richard Sauerheber, a chemistry professor in San Diego, that not all reverse osmosis (R-O) systems achieve satisfactory results. Sauerheber tested the effectiveness of various R-O systems and found that the efficiency of removing fluoride varied significantly among systems, and seemed to depend, in part, on the flow rate of the water. In others, the greater the flow of water through the system, the less effective they were at removing fluoride. We have no way of verifying the accuracy of Sauerheber’s results, but we believe they are worth considering.

2) Bone Char Filters

The filters that Suauerheber found to be the most effective at removing fluoride were “bone char” filters. This is a filter that has been used on a large scale in some areas of the world with widespread fluoride poisoning (e.g., India). They might, however, be difficult to get hold of in western countries.

3) If You Purchase a Deionizer, Make Sure It Uses an “Ion Exchange Resin.”

If you are considering purchasing a filter that uses deionization, make sure that it uses an “ion exchange resin.” If it does not use an ion exchange resin, it will not remove the fluoride.

4) Make Sure to Properly Maintain the Filter

Whichever filter you do end up purchasing, pay close attention to the instructions on how to properly maintain it. Each type of filter, for example, requires that you replace the filter cartridge at regular intervals. If this is not done, the effectiveness of the filter will significantly decline.

5) An Advantage of Deionizers with Ion Exchange Resins

There is advantage to ion exchange resins that we believe is worth mentioning. But, first, by way of background, it will be helpful to explain the difference between how ion exchange resins differ from reverse osmosis.

In an R-O system, the fluoridated water is forced at high pressure through a membrane. The fluoride ions, with a sheath of water molecules, are too large to pass through the small pores in the membrane and only the water can get through. Thus virtually pure water is squeezed through the membrane.

By contrast, an ion exchange resin consists of both a cation exchange resin (which exchanges a positive hydrogen ion for any metal ions present) and a negative exchange resin (which exchanges a hydroxyl ion for the fluoride ion). When both resins are used together the hydrogen ions produced by one resin and the hydroxyl ions produced by the other instantly combine to form water. The distinct advantage of this system is that when either resin is saturated, ions will appear in the collected water, which will immediately and dramatically increase the electrical conductivity of the solution and thus be readily detectable by a very cheap monitoring system. FAN’s Director, Paul Connett, personally observed the operation of an ion-exchange resin system when he stayed with Dr. Mark Diesendorf in Sydney, Australia, and was impressed with its efficiency. According to Connett, “The flow rate was very fast and Mark could quickly collect several bottles for his use throughout the day as well as taking a bottle or two to work the next morning.”

Another advantage of using ion exchange resins is that it’s less wasteful of both energy and water than R-O.