Section 27-917. Existing soil and vent stacks

(a) When a new building is
  erected higher than an existing building, no operable windows  or  other
  wall openings shall be located closer than ten feet to an existing stack
  vent  or vent stack on the lower building. Wherever necessary, the owner
  of the new building shall at  his  or  her  own  expense  and  with  the
  approval  of the adjoining owner, offset the stack vent or vent stack to
  a distance ten feet or more from such windows or wall opening, or  shall
  extend  such  stack  vents  or vent stacks to a height of at least three
  feet above the topmost opening.
    (b) When the existing  adjoining  building  is  higher  than  the  new
  building,  all new soil, waste, or vent stacks of the new building shall
  be located at least ten feet from the  common  lot  line,  or  shall  be
  carried  to a level above the higher existing roof, adequately supported
  and with the consent  of  the  owners  of  both  the  new  and  existing
  structures.