EI 11C201
CEMP-E
1 March 1997
(3) In areas where problems with root penetration are anticipated (local experience is a
good guide), pipe which has the kind of joint which will successfully resist root penetration shall
be specified. Generally speaking, the more water tight the joint, the greater will be the resistance
to root penetration. Rubber-gasketed and compression-type joints are considered to provide the
tightest joints. Also it is best to use pipe which comes in long lengths.
b. Ductile iron. Ductile iron (D.I.) pipe is suitable for sewers and force mains used at
pumping stations and wastewater treatment facilities. Special uses include river crossings, pipe
located in unstable soil, highway and rail crossings, and pipinginstalled above ground. D.I. pipe
is susceptible to corrosionfrom acid wastes and aggressive soils. Cement, polyurethane,
bituminous, or polyethylene linings are usually providedfor interior protection. However cement is
not adequate for highly aggressive acid atmospheres; in such environments, pure fused calcium
aluminate with pure fused calcium aluminate aggregates is recommended in lieu of standard
cement lining. (See Section 11-3, Cement Lining.) For extremely corrosive soils,polyethylene
encasement in accordance with AWWA C105 is recommended for external protection. Cathodic
protection can be provided but is generally not cost effective when compared to polyethylene
encasement. Pipe is available in 80 mm (3-inch) through 1,350 mm (54-inch) diameters, in 5-1/2
or 6 meter (18 or 20-foot) lengths, and with mechanical, push-on, or flanged joints. Flanged
joints are restricted to interior or above ground piping. Allowable trench and superimposed
surface loads for D.I. pipe are computed and tabulated in ANSI A21.50. The ordinary range of
loading can be met without special bedding materials and procedures.
c. Steel. Steel pipe may be used for force mains when lined with cement mortar, bituminous
materials, or polyurethane to provide internal protection. A bituminous coating must be applied
for externalprotection also. Lined and coated steel pipe is available indiameters 100 mm (4-inch)
through 3,600 mm (144-inch). Galvanized steel pipe will only be used for small diameter force
mains and pressure sewers from 32 mm (1-1/4-inch) to 100 mm (4-inch) in size. Joints for steel
pipe less than 150 mm (6-inch) will be threaded. Pipe 150 mm (6-inch) in diameter and larger
will have mechanical, push-on or flanged joints. Threaded and flanged joints will be used only for
interior piping. Steel pipe will be installed in accordance with the manufacturer's
recommendations, and Manual No. M11 - Steel Pipe Design and Installation published by the
American Water Works Association (AWWA).
d. Cast iron. Cast iron soil (C.I.S.) pipe will normally be allowed only as an option for building
connections. C.I.S. pipe is used primarily for building interior drainage, waste, and vent piping,
as described in Chapter 1 of the Cast Iron Soil Pipe & Fittings Handbook published by the Cast
Iron Soil Pipe Institute. C.I.S. pipe is resistant to internal and external corrosion when provided
with a bituminous coating, and is not subject to abrasion from grit, sand, or gravel. Factory
applied bituminous coatings need to be inspected after the pipe is installed and recoated as
needed. C.I.S. pipe is available in 50 mm (2-inch) through 380 mm (15-inch) diameters, in 1.5 m
(5-foot) and 3 m (10 foot) laying lengths, and is manufactured in service (SV) and extra heavy
(XH) classifications. Pipe joints will be either compression type using rubber gaskets, or bell and
spigot type caulked with lead and oakum. Structural design of C.I.S. pipe will be in accordance
with the methods outlined in chapter 5 of the Cast Iron Soil Pipe & Fittings Handbook, with
special emphasis given to external loadings and pipe strength.
e. Concrete. Concrete pressure pipe and sewer pipe is appropriate for applications requiring
large diameter or high strengths. A disadvantage is the lack of corrosion resistance to acids,
especially critical where hydrogen sulfide is generated in substantial quantities. However, special
PVC or clay liner plates, coatings of coal-tar, coal-tar epoxy, vinyl, or epoxy mortar can be applied
to the pipe for corrosion protection. Concrete pipe joints are either bell and spigot type using
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