A method of manufacturing bulked continuous carpet filament from polytrimethylene terephthalate (PTT) with polyethylene terephthalate (PET) comprises: (1) splitting the PTT stream extruded from the primary extruder into a number of polymer streams, each of the plurality of polymer streams having an associated spinning machine; (2) adding a colorant to each split polymer stream; (3) adding PET to the extruded polymer stream downstream of the primary extruder; (4) using one or more static mixing assemblies for each split polymer stream to substantially uniformly mix each split polymer stream and its respective colorant and PET; and (5) spinning each polymer stream with its substantially uniformly mixed colorant and any additives into BCF using the respective spinning machine.