Underground piping outside of buildings maybe cast-iron soil pipe, vitrified clay or concrete,or plastic polyvinyl chloride (PVC) pipe, but PVCpipes are the most common. Undergroundpiping within buildings may also be of cast iron,galvanized steel, lead, or PVC; however, cast ironand PVC are the most popular materials used.Aboveground sewage piping within buildingsconsists of either one or a combination of thefollowing: brass or copper pipe, cast iron orgalvanized wrought iron, galvanized steel or lead,and PVC pipe. Again, the reason for thegrowing popularity of plastic PVC piping is theunique combination of chemical and physicalproperties it has, ease of installation, and costeffectiveness. Descriptions and characteristics ofsome of the most common piping materials usedin a sanitary drainage system follow.CAST-IRON SOIL PIPE (CISP).— This typeof pipe is composed of gray cast iron made ofcompact, close-grained pig iron; scrap iron andsteel; metallurgical coke; or limestone. Cast-ironsoil 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 orother places of heavy traffic. If the soil is unstableor contains cinder and ashes, vitrified clay pipeis used instead of cast-iron soil pipe.Cast-iron soil pipe comes in 5-ft and 10-ftlengths, with nominal inside diameters of 2, 3, 4,5, 6, 8, 10, 12, and 15 in. It is available assingle-hub or double-hub in design, as indicatedin figure 8-13. Note that single-hub pipe has a hubat one end and a spigot at the other, while aFigure 8-13.-Single-hub and double-hub cast-iron soil pipe.double-hub pipe has a hub on each end. Hubs orbells of cast-iron soil pipe are enlarged sleevelikefittings that are cast as a part of the pipe to makewatertight and pressure-tight joints with oakumand lead.VITRIFIED CLAY AND CONCRETEPIPE.— Vitrified clay pipe is made of moistened,powdered clay. It is available in laying lengths of2, 2 1/2, and 3 ft and in diameters ranging from4 to 42 in. Like cast-iron soil pipe, it has a bellend and a spigot end to facilitate joining. Vitrifiedclay pipe is used for house sewer lines, sanitarysewer mains, and storm drains.Precast concrete pipe may be used for sewersin the smaller sizes—those less than 24 in. Thispipe is not reinforced with steel. Dimensions ofconcrete pipe are similar to those of vitrified claypipe.PLASTIC PIPE.— The use of rigid plasticpipe has expanded greatly over the years. Yearsago, plastic piping was used extensively for farmwater systems, lawn sprinklers, and some otherdomestic and industrial uses. Now, plastic pipeis used for all kinds of water and drainageapplications.Plastic piping has outstanding resistanceto nearly all acids, caustics, salt solutions,and other corrosive liquids and gases. Itdoes not rust, corrode, scale, or pit insideor outside. It is also nontoxic, nonconductive,and not subject to electrolytic corrosion—amajor cause of failure when metal pipe isinstalled underground. Another important advan-tage of plastic pipe is low resistance to abrasionbecause of its smooth inner wall, resulting inmaximum flow rate and minimum buildup ofsludge and slime.FittingsThe types of fittings, joints, and connectionsused by water distribution are strikingly similarto those used by waste drainage systems. Insanitary or waste drainage systems, fittings alsovary according to the type of piping materialsused; however, special mechanical seal adaptersare available for joining different types ofpipes, such as cast-iron soil pipes to vitrifiedclay, or vice versa. Some of the fittings commonly8-11
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