A water filtration system (100) includes: a raw-water inlet (100a); a pure-water outlet (100b); a purified-water outlet (100c); a waste-water outlet (100d); an integrated filter cartridge (1); and a return flow path (101). The integrated filter cartridge (1) has a first port (10a), a second port (10b), a third port (10c) and a fourth port (10d). The purified-water outlet (100c) and the waste-water outlet (100d) both are connected to the third port (10c), and a water storage device (2) is provided to at least one of the fourth port (10d) and a flow path connected to the pure-water outlet (100b). The return flow path (101) has a first end connected between the first port (10a) and the raw-water inlet (100a) and a second end connected between the waste-water outlet (100d) and the third port (10c).