53 Pa. Stat. § 14847
Water-closets when located in yard must be arranged as to be conveniently and adequately flushed, and the water-supply pipes and traps protected from freezing by being placed in a hopper-pit, at least four feet below the surface of the ground, the walls of which pit shall be constructed of hard burned brick or stone laid in cement or mortar, or of concrete, and traps used inside pit must be extra heavy cast-iron, and the trap to have a hand-hole for cleanout purposes. The closet drain to be vented, with a four-inch pipe and carried up above the roof of closet, away from any opening or window. The water shall be supplied through an automatic seat-action valve. The waste water from value shall be conveyed to the sewer through a half-inch lead pipe, properly connected. The enclosure of yard water-closets shall be ventilated by slatted openings, and there shall be a trap-door in floor of sufficient size to permit of convenient access to the hopper-pit.
53 P.S. § 14847