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I I I I I I I I I I I I I I I I I I I Ouctile iron pipe is subject to corrosion in some environments. The Ductile Iron Pipe Research Association (OIPRAl claims that in corrosive environments tluctile iron pipe can be protected by encasing the pipe in an inexpensive polyethylene sleeve. The polyethylene sleeve is often utilized even in non-corrosive environments because of the inexpensive protection it provides. The effectiveness of the polyethylene sleeve in extremely hostile environments is subject to some debate. OIPRA claims that reported bad experience with the sleeve is due to improper sleeve installation. Traditional cathodic protection systems can also be applied to ductile iron pipe installations. Ouctil e iron pi pe is consi dered a ri gi d pi pe in si zes from 4 to 20 inches in diameter and requires no pipe zone backfill material during installation. 3.5.5 Pipe Type eomparfsons Table 3.9 summarizes the general comoarison of the above mentioned oipe types. After considering the characteristics of the various types of pipe materials, some conclusions can be made as follows:. o Oucti1e iron is a good pipe. The most serious question regarding the suitability of ductile iron relates to its corrosi on resi stance. With regard to ease of hand1 i ng, flow capacity, and strength, ductile iron is very acceptable for the Towaoc water line. o The fi berg1 ass pipe "Permastran" is acceptabl e for use in the Towaoc water line. Its only serious technical drawback is that it is only available, on a cost effective basis, in sizes up to 12 inches. If some 14-inch pipe is required, Permastran could only be used for the 12-inch portion of the line. Permastran would be a viable choice for use in line segments where soil corrosivity is a concern. Its backfill requirements however will be more demanding and expensive than those of ductile iron or concrete pipe. 3-22 l060c