Abstract: A pourspout accessory kit for use with a portable toilet holding tank to facilitate dumping of the holding tank's contents via an outlet opening in the holding tank. The accessory kit copmrises a pourspout having an inlet end for attachment to the holding tank outlet opening and an outlet end spaced from the inlet end. Respective inlet and outlet end closure caps cover the inlet and outlet ends respectively of the pourspout. The inlet end of the pourspout is configured to fit a holding tank outlet opening having either a partial internal screw thread or a full external screw thread. The attachment to the partial internal screw thread is by means of a pair of bayonets on diametrically opposite sides of the pourspout which engage the partial screw threads on diametrically opposite sides of the holding tank outlet opening.