a continuous flow polymer filtration apparatus for replacing dirty filters in an extruder includes a reciprocating slide member secured within a slide channel transverse to a bore . the slide channel has a sealing region adjacent to the bore . the slide member houses two filter assemblies for filtering polymer . each filter assembly comprises at least one filter element which has a width that is less than the width of the sealing region and the distance between the filter assemblies is less than the width of the bore . the slide member is capable of positioning either filter assembly in line with the bore without interrupting the fluid flow of the polymer as well as positioning either filter assembly off - line in order to replace the off - line filter assembly .