Abstract: A three way cock for filter press plates comprising a cock body defining a cylinder portion, a foot portion extending parallel to the cylinder portion, for applying the cock to the side of the plate, and a flange portion connecting the cylinder portion and foot portion through which extend a pair of fluent passages that connect the bore of the cylinder portion, and upper and lower ports formed in the cock cylinder portion with correspondingly located fluent passages of the plate. The cock cylinder portion has reciprocably mounted in same a spool valve member that shifts longitudinally of the cylinder portion under the action of opposed cam surfaces formed in the cylinder portion, and an end cap received over the upper end of the cylinder portion through which the valve member extends for keying connection to an operating knob for turning the valve member to move it between the three operating positions of the cock.