The best type of filter cartridge for a water purifier is a combination of a sediment filter, a carbon block filter, and an ion exchange filter. This combination effectively removes a wide range of contaminants, including particulates, organic chemicals, and heavy metals. According to the Environmental Protection Agency (EPA), sediment filters can remove particles as small as 1 micron, carbon block filters can reduce chlorine, taste, and odor, and ion exchange filters can remove dissolved minerals like lead and arsenic. This multi-stage approach ensures comprehensive purification, providing clean and safe drinking water.