Cement -lined at www.japanese-home-gardens.com

While various materials were formerly used for pipes—wood, wrought iron, cement -lined-lined stovepipe, wrought steel, steel plate, reinforced concrete, galvanized steel, and cast iron—the present trend is to use cast-iron pipe (cement -lined lined in regions where the water is aggressive) or asbestos-cement -lined pipe. The sizes of pipe where hydrants are to be served should never be less than 8 inches, except in small, limited systems. Street mains larger than 48 inches are uneconomical, although 72-inch pipes are sometimes used, as in Jersey City and in Brooklyn. Large cast-iron pipes are subject to shrinkage and other stresses, which make them less reliable than steel or reinforced concrete in cases of heavy pressure or traffic loads.

The resulting cement -lined, produced from the formerly discarded grappiers, was of much higher quality than that obtained from the unsintered material. This fact was firmly established by the English cement -lined manufacturer L. C. Johnson in 1845, and the term "portland cement -lined" has since been applied solely to the cement -lined made from the sintered material. This period marks the real beginning of the portland cement -lined industry.

Reinforced-concrete conduits may be monolithic, precast, or prestressed. Precast pipe is made in sizes up to 180 inches. Steel cylinder pipe is recommended where the head exceeds 100 feet. Prestressed concrete steel cylinder pipe is available in sizes 24 to 144 inches; it requires a better grade of steel, but only 70 to 80 percent of the amount needed in non-prestressed pipe; concrete is of better quality, and Wall thickness can be reduced. The hydraulic carrying capacity of concrete, asbestos cement -lined, or cement -lined-lined metal pipes does not deteriorate as rapidly as in tar-coated metal pipe; however, slimes will build up in such pipes and reduce the carrying capacity.