A water filtration system (100) includes a filter cartridge assembly (10), a water-inlet conduit (20), a purified-water conduit (30), a pure-water conduit (40) and a waste-discharge conduit (50). The filter cartridge assembly (10) has a water inlet (110), a purified-water outlet (120) and a purified-water outlet (140). The water-inlet conduit (20) is in communication with the water inlet (110). The pure-water conduit (40) is in communication with the pure-water outlet (140). The purified-water conduit (30) is in communication with the purified-water outlet (120) and has a first valve body (320) configured to control on and off of the purified-water conduit (30). The waste-discharge conduit (50) is in communication with the purified-water conduit (30).