Underground piping outside of buildings may
be cast-iron soil pipe, vitrified clay or concrete,
or plastic polyvinyl chloride (PVC) pipe, but PVC
pipes are the most common. Underground
piping within buildings may also be of cast iron,
galvanized steel, lead, or PVC; however, cast iron
and PVC are the most popular materials used.
Aboveground sewage piping within buildings
consists of either one or a combination of the
following: brass or copper pipe, cast iron or
galvanized wrought iron, galvanized steel or lead,
and PVC pipe. Again, the reason for the
growing popularity of plastic PVC piping is the
unique combination of chemical and physical
properties it has, ease of installation, and cost
effectiveness. Descriptions and characteristics of
some of the most common piping materials used
in a sanitary drainage system follow.
CAST-IRON SOIL PIPE (CISP).— This type
of pipe is composed of gray cast iron made of
compact, close-grained pig iron; scrap iron and
steel; metallurgical coke; or limestone. Cast-iron
soil pipe is normally used in or under buildings,
protruding at least 5 ft from the building. Here,
it connects into a concrete or clay sewer line.
Cast-iron soil pipe is also used under roads or
other places of heavy traffic. If the soil is unstable
or contains cinder and ashes, vitrified clay pipe
is used instead of cast-iron soil pipe.
Cast-iron soil pipe comes in 5-ft and 10-ft
lengths, with nominal inside diameters of 2, 3, 4,
5, 6, 8, 10, 12, and 15 in. It is available as
single-hub or double-hub in design, as indicated
in figure 8-13. Note that single-hub pipe has a hub
at one end and a spigot at the other, while a
Figure 8-13.-Single-hub and double-hub cast-iron soil pipe.
double-hub pipe has a hub on each end. Hubs or
bells of cast-iron soil pipe are enlarged sleevelike
fittings that are cast as a part of the pipe to make
watertight and pressure-tight joints with oakum
and lead.
VITRIFIED CLAY AND CONCRETE
PIPE.— Vitrified clay pipe is made of moistened,
powdered clay. It is available in laying lengths of
2, 2 1/2, and 3 ft and in diameters ranging from
4 to 42 in. Like cast-iron soil pipe, it has a bell
end and a spigot end to facilitate joining. Vitrified
clay pipe is used for house sewer lines, sanitary
sewer mains, and storm drains.
Precast concrete pipe may be used for sewers
in the smaller sizes—those less than 24 in. This
pipe is not reinforced with steel. Dimensions of
concrete pipe are similar to those of vitrified clay
pipe.
PLASTIC PIPE.— The use of rigid plastic
pipe has expanded greatly over the years. Years
ago, plastic piping was used extensively for farm
water systems, lawn sprinklers, and some other
domestic and industrial uses. Now, plastic pipe
is used for all kinds of water and drainage
applications.
Plastic piping has outstanding resistance
to nearly all acids, caustics, salt solutions,
and other corrosive liquids and gases. It
does not rust, corrode, scale, or pit inside
or outside. It is also nontoxic, nonconductive,
and not subject to electrolytic corrosion—a
major cause of failure when metal pipe is
installed underground. Another important advan-
tage of plastic pipe is low resistance to abrasion
because of its smooth inner wall, resulting in
maximum flow rate and minimum buildup of
sludge and slime.
Fittings
The types of fittings, joints, and connections
used by water distribution are strikingly similar
to those used by waste drainage systems. In
sanitary or waste drainage systems, fittings also
vary according to the type of piping materials
used; however, special mechanical seal adapters
are available for joining different types of
pipes, such as cast-iron soil pipes to vitrified
clay, or vice versa. Some of the fittings commonly
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