expressed in drainage fixture units, would be
calculated as follows from table 7-2.
Number and Type
22 lavatories (1 1/4-inch 1
15 shower heads
20 urinals (wall)
2 sinks (service)
4 floor drains (2-inch)
After calculating the total discharge and deter-
mining the slope of the piping and the velocity
of flow, select the correct size of pipe by using
table 7-3. Assume that the cast-iron house drain
to be installed will have a slope of 1/4 inch per
foot. From table 7-3, the minimum size pipe for
the horizontal sanitary drainage system under
discussion is 5 inches.
Table 7-3 is for cast-iron soil pipe or gal-
vanized steel pipe house drains, house sewers, and
waste and soil branches. When copper tubing is
used, it may be one size smaller than shown in
the table. Note that the size of building drainage
lines must never decrease in the direction of flow.
When provision is made for the future installa-
tion of fixtures, those provided for must be con-
sidered in determining the required sizes of
drainpipes. Construction to provide for such
future installation should have a plugged fitting
or fittings at the stack to eliminate any dead ends.
Sizing Stacks and Branches
The term stack is used for the vertical line of
soil or waste piping into which the soil or waste
branches carry the discharge from fixtures to the
house drain. A waste stack carries liquid wastes
that do not contain human excrement; a soil stack
carries liquid wastes that do.
Most buildings do not have separate soil and
waste stacks. A single stack known as the soil and
waste stack, or simply the soil stack, serves to
carry both soil and waste material. Soil stacks are
usually made of cast-iron pipe with caulked joints.
They may, however, be made of other materials
Table 7-3.Maximum Loads for Horizontal Drains