A filter system and method of filtering a feed liquid utilizing a combined plurality of filter assemblies. Each filter assembly includes a filter housing, a filter cartridge and a spiral passageway for imparting secondary flow currents, particularly Dean-Flow currents, to fluid flowing within the spiral passageways to prevent particulate build-up on filter surfaces so as to extend filter life and duration between replacement. The filter system can be operated within positive or negative pressure filtration processes. A dual-stage filtration process utilizing a cap filter and a cylindrical depth filter is also disclosed.