stack 100 is contained in a stack box 50 once the stack 100 is installed through each interval as depicted in fig2 in this manner the molded stack unit is contained in a box wherein the box length is determined by the number of plumbing fixtures served by the box and the box width is determined by the pipe diameters of the branch pipes 40 stack waste riser 10 and stack vent riser 20 as depicted in fig5 a plurality of stack boxes 50 are correspondingly installed vertically and interconnected to the desired level of high rise construction wherein each interval of high rise construction vent stack has at least one box an example of stack box 50 sizing according to the present invention would be where the connectors 30 to the stack waste riser 10 and stack vent riser 20 are two inch diameter pipes on five inch center lines the stack vent riser 20 and stack waste riser 10 are each four inches in diameter on a three inch center line from each respective edge of the stack box 50 for these dimensions the stack box 50 would require a length of twenty eight inches and a width of six inches typical water closet lavatory and bath tub fixture groups in the art with individual cans for the plumbing riser would require at least forty four inches in length using a separate.