N.Y.C. Admin. Code § 27-917: § 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.