Each drainage stack that extends 10
or more stories shall be served by a parallel vent stack, which
shall extend undiminished in size from its upper terminal and
connect to the drainage stack at or immediately below the
lowest fixture drain. Each such vent stack shall also be connected
to the drainage stack at each fifth floor, counting down
from the uppermost fixture drain, using a yoke vent, the size
of which shall be not less in diameter than either the drainage or the vent stack, whichever is smaller.