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Carbon Block, Reverse Osmosis, Charcoal, KDF, Granulated Activated Carbon

Most commonly customers justifiably worry about variety of water filtration methods and the effective way the work. When an individual goes to the shop in order to purchase a water cleansing device, dealers offer him a wide and motley range of filters and a complicated task to choose from carbon block, KDF, reverse osmosis, and even distillation – as from the range of most popular. We have written the following material in attempt to describe these methods in some close details and then find the common and the different features among them to help you choose a right one when you have a problem with purchasing a water filtration system for your own.

Carbon Block

During the process of carbon block filtration water is taken through the pores of heavy arranged carbon block, where with the help of mechanical filtration, physical/chemical adsorption and elecrokinetic adsorption water is relieved from a number of common harmful substances. Taste and smelling issues, chlorine, particulate substances and a number of other contaminants, which interfere health stability – VOCs (herbicides, pesticides and chemicals), cysts (giardia and cryptosporidium), some endocrine contaminants, heavy metals (mercury, lead), Trihalomethanes (by-products of disinfecting process which cause cancer), MTBE, turbidity, asbestos and Chloramines can be cleansed with the help of Solid Carbon Block method. Solid carbon block filters don't wash away natural and healthful minerals, don't require electrical power and don't put silver or salt into the filtered water.

Reverse Osmosis

Reverse osmosis (RO) as a method of filtering was created more than a century ago, but it hasn't turned into commercial use before a certain device was worked out in the early sixties (1,2,3,4). As RO is active at a comparably low temperature and its energy consumption is rather economic, people use it with different applications, for example, cleansing of polluted water, desalination, minerals' reclamation, regulating percent of whey and various food products and water filtration. RO has an advantage – it washes away some harmful substances, which carbon block filters can't (for example nitrates or fluoride), but it also has disadvantages. They are: Reverse osmosis isn't able to cope with most of Volatile Organic Chemicals (VOC's); its performance is very low – you need over 24 hours to produce 5 gallons of pure water, you must have a holding volume to keep the purified water; significant volumes of water are lost – for every gallon filtered you have 3 to 9 gallons lost; it also washes away trace components and minerals which are necessary for organism's health.

During the RO procedure, dirty water is taken through a prefilter after pH checking, and then put into membrane cells at the corresponding pressure. Then the water produced is taken to a storage volume and harmful substances are washed away (6). Most RO devices with a cellulose acetate membrane are worked out to act between 55 F – 86 F (13 C – 30 C). Actually, the dirty water can pass through one of or a set of the following points: chlorinator and retention volume, anthracite filter, degasifier, neutralizer, sand bed, activated charcoal filter, microfilter, and deionizer, it depends on the kind of filtered water and the quality of water you want to receive after filtration. As the degree of water dirtiness can differ from case to case, you need corresponding pretreatment for the bacterial level of dirty water and dissolved solids can be put under control after the prefiltration within the scheduled frames. Other words, RO should be mixed with other methods as granulated activated carbon and carbon block in order to receive corresponding filtration and safe water as a result.

Charcoal or Granulated Activated Carbon (GAC)

This kind of filters includes granulated or powdered components, which lead water around but not through the carbon. They are classified as taste and smell filters for the short contact the carbon has with water.


In the KDF device water comes through a set of applications made of a certain pure alloy blend of two different metals – zinc KDF-55D and copper. This method, protected by KDF Fluid Treatment patent in 1987, is the most popular and the most called for method of water filtering which acts on the spontaneous-oxidation-reduction (redox) and electro-chemical basis. Chlorine is immediately and almost finally oxidized.


It's similar to Charcoal Filters mentioned, but it also uses silver to prevent bacteria growth when the water stays in filter.
Silver taken in abnormal doses is harmful for human's organism; that's why it should pass registration with the EPA as including a harmful component.

Limited Media Filters

As people more and more have a demand for quality of the water they drink, new kinds of applications will be tested by the market, from coconut shells to metal shavings. Some components can easily be inactive in washing away certain contaminants in the water, but there's a large number of these contaminants to reduce.

Filtration Media

Reverse Osmosis Carbon Block KDF Carbon (GAC)
Contaminant/Additive Reduction        
TDS Yes Some No Some
Chlorine Yes Yes Yes Yes
Fluoride Yes No No No
VOC's No Yes No Some
Nitrates Yes No No No
Microbes and Bacterials No Yes No Some
Metals Yes Some Some Some
Other Features        
Mineral Content Eliminates Retains Retains Retains
Water Waste High Waste None None None
Price Higher Variable Low Variable
Maintenance Costs High Low Low Variable

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