53 Pa. Stat. § 25024
In every tenement house hereafter to be erected, whenever a connection with a public sewer is in any way possible (and of this possibility the bureau of health shall be the sole judge), 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 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. In every now existing tenement house there shall be (subject to the possibility of connection with public sewer, as above set forth) at least one water closet for every two apartments. 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. And every such water closet shall be properly ventilated, in accordance with the regulations governing the same already in force in said cities. When necessary (and of this necessity the said bureau of health shall be the judge) such water closets may be located in the yard. Wherever located, the said water closets shall conform in design, materials and construction to the building and health regulations of said cities.
53 P.S. § 25024