The house sewer shall be laid straight on a uniform grade and on a firm bed. The minimum gradient for the house sewer shall be 1/8 inch per foot for pipe 6 inches in diameter or larger, and 1/4 inch per foot for cast-iron pipe 4 inches or 5 inches in diameter, all with a maximum gradient of 1/2 inch per foot. Bell holes shall be dug so that the bell and spigot shall not rest on the sockets. The bell end of the pipe shall be laid upgrade.
('69 Code, § 20-88)