The jug filter is a flow filter. The water is purified while it flows through the cartridge by gravity. In Aquaphor water filter jugs, activated carbon and resin are mixed with Aqualen fiber (the company's patented invention). Thanks to Aqualen, the cartridge lasts longer, and the water cannot wash its "channels" and pass without cleaning: Aqualen holds the granules tightly together, like the roots of a tree do the soil.