In every such tenement house there shall be one water closet for every tenement or suite of rooms which has its own independent hallway, so separated that its rooms do not open into or connect with any other rooms; and in tenement houses so constructed that a tenement may consist of a single room, or of two rooms, there shall be at least one water closet for every three rooms: Provided, That in the case of buildings existing at the date of this act which shall hereafter be altered into tenement houses there shall be one water closet for six rooms, but not less than one for each floor. Every water closet shall be separated from every other water closet and shall have an entrance entirely independent of the entrance to every other water closet. There shall also be an independent water supply, and at least one sink for every tenement or suite of rooms. No hydrant shall be permitted in the yard or open space provided for in the second section of this act.¹