A self-cleaning filter apparatus for filtering a primary flowing fluid, the apparatus adapted to be connected to a supply line for the primary flowing fluid, the self-cleaning filter apparatus selectively operable in a filter mode and a self-cleaning mode, the apparatus comprising: a. a housing having an inlet on the upstream side to receive unfiltered flowing fluid, and an outlet on the downstream side to deliver clean filtered fluid, b. a plurality of filtering elements encased by said housing and serving to filter said flowing fluid as the fluid flows from said upstream inlet to the downstream outlet, said filtering elements provided in the form of disc filters are arranged on a spine assembly, and c. a piston assembly controlled according to differential pressure between said inlet and said outlet and configured to facilitate un-stacking of said filtering elements during self-cleaning and stacking of said filtering elements during filtering; d. said spine assembly including at least one tubular conduit having an open end configured to be in fluid communication with said downstream outlet during the self-cleaning mode to receive a flow of downstream flowing fluid from said downstream outlet during self-cleaning mode, said tubular conduit having a plurality of nozzle spray openings distributed along its length and configured to produce tangential fluid stream of said downstream flowing fluid to clean said plurality of filtering elements during self-cleaning mode; e. the spine assembly characterized in that said at least one tubular conduit having an open end is coupled with a venturi member assembly at said open end, the venturi member assembly comprising a venturi element provided to introduce at least one secondary flowing fluid at said open end during said self-cleaning mode utilizing the venturi effect and wherein said secondary flowing fluid is atmospheric air disposed external to said filter apparatus and wherein said venturi member assembly is configured to introduce said secondary flowing fluid during self-cleaning without utilizing pumps and/or compressors across said housing at said open end. a. a housing having an inlet on the upstream side to receive unfiltered flowing fluid, and an outlet on the downstream side to deliver clean filtered fluid, b. a plurality of filtering elements encased by said housing and serving to filter said flowing fluid as the fluid flows from said upstream inlet to the downstream outlet, said filtering elements provided in the form of disc filters are arranged on a spine assembly, and c. a piston assembly controlled according to differential pressure between said inlet and said outlet and configured to facilitate un-stacking of said filtering elements during self-cleaning and stacking of said filtering elements during filtering; d. said spine assembly including at least one tubular conduit having an open end configured to be in fluid communication with said downstream outlet during the self-cleaning mode to receive a flow of downstream flowing fluid from said downstream outlet during self-cleaning mode, said tubular conduit having a plurality of nozzle spray openings distributed along its length and configured to produce tangential fluid stream of said downstream flowing fluid to clean said plurality of filtering elements during self-cleaning mode; e. the spine assembly characterized in that said at least one tubular conduit having an open end is coupled with a venturi member assembly at said open end, the venturi member assembly comprising a venturi element provided to introduce at least one secondary flowing fluid at said open end during said self-cleaning mode utilizing the venturi effect and wherein said secondary flowing fluid is atmospheric air disposed external to said filter apparatus and wherein said venturi member assembly is configured to introduce said secondary flowing fluid during self-cleaning without utilizing pumps and/or compressors across said housing at said open end.