For house sewers, 4- and 6-inch pipes are generally used. Where a
4-inch pipe is used, cast-iron is commonly recommended. Grades with
little fall require larger pipes. The large sizes are also less liable
to become clogged. Clay pipe is made in pieces 2 or 2-1/2 feet long,
whereas fiber-pipe sections are 4 feet long and cast-iron pipe 5 feet
long, so that there are fewer joints. The minimum number of joints is
desirable, as there is less danger of stoppage.