: How does activated carbon in the filters clean our water? : The materials for making activated carbon include plant, animal, or even minerals. The most commonly used materials are charcoal and coconut shells, which goes through an activated process and becomes activated carbon with absorbent qualities. Granular activated carbon is filled with countless vesicles of different sizes and diverse paths, which maximizes the surface area. Impurities are caught when passing through these vesicles and the walls inside the granulated activated carbon absorb all kinds of organic matters, thereby purifying the water.     : What other materials are needed for filtering apart from activated carbon? : Activated carbon can remove chlorine, organic pollutants like pesticides, industrial solvents and odours, but is not effective for removing microorganisms and soluble metal. Accumulated impurities (including some organic matters and some bacteria) can provide nutrients to bacteria and therefore cartridges can be the breeding ground of bacteria. Advanced filters therefore use Kinetic Degradation Fluxion in addition to activated carbon.     : What is KDF? : KDF stands for Kinetic Degradation Fluxion and is the only pesticidal device designated by Environmental Protection Agency to be used in water filters. KDF is the alloy of highly concentrated copper and zinc particles, with its major functions being removing soluble metals like lead and mercury in water, as well as suppressing bacteria growth i.e. bacteriostatic. KDF can raise the effectiveness of activated carbon by 5 times and therefore has been very widely adopted in water filters since its introduction in 1992.     : Are there any water filters that do not require changing cartridges? : No. Sediments and impurities in water accumulates with filtering and cartridges have to be changed regularly to maintain its effectiveness. However, some water filters use a sealed design, can accommodate more filtering materials, therefore increase capacity and lengthen the life of the filters. Generally, these kinds of filters can filter tens of thousands of gallons of water and its life can be as long as 3 years! Of course, with time and the cartridge saturated, the filter has to be changed. This kind of filter does not have any cartridge and therefore are sometimes misunderstood to be free from cartridge-change. Some water filters are capable of back-washing. Impurities like silt and corrosives on the surface of activated carbon can be washed out and lengthen the life of the water filter. However, similar to recharging batteries, the filtering materials will gradually lose its effectiveness and the filter would have to be replaced in a certain length of time, say 2 to 3 years.     : Why is there a need for pre-filter and main filter in Vancouver? : Vancouver's water contains a high amount of silt. It can easily block the cartridge and slow down water flow. Prefilters use special fibre to remove the tiniest impurities and silt. These fibre cartridges are cheaper and can be changed more frequently. The main filter cartridge are more expensive and it is more sensible to lengthen its life by avoiding blockage. This is why two-cartridge filters are more cost-effective in Vancouver.