Abstract: An improved polymer processing system having a pair of filtration units and a diverter valve arrangement for directing the flow of molten polymers alternately through the filtration units includes an improved manifold for the diverter valve arrangement for positioning the filtration units at opposite sides of the diverter valve arrangement allowing connection between the diverter valve arrangement and the filtration units with relatively shorter connecting pipes. The improved polymer processing system also includes an improved vent valve arrangement extending through the lid of the filtration unit and a means for introducing gas into an inactive filtration unit for speeding the draining of the polymer from the unit. The improved polymer processing system also includes a means for protecting the annular seal of the inlet port of each filtration unit during the process of reinstalling the filter vessel into the surrounding jacket.