The effluent sewer should be constructed in similar manner and of the
same materials as the house sewer and on a slope of 1/8 inch to 1 foot.
This line, however, may be laid of terra-cotta pipe, as cast-iron is
not considered necessary except in unusual cases. This line should
always terminate in a distribution box from which the tile lines
of the disposal field lead away. For steep slopes the arrangement
shown in figure 9 (p. 15) is practical. Joints must be of root-tight
construction if the sewer is in the vicinity of trees or shrubs. The
length of the sewer depends upon the distance from the tank to a safe
site for the disposal field.