Experience With Main Breaks in Four Large Cities: <i>Panel Discussion</i>: Fid-Bau Portal

Experience With Main Breaks in Four Large Cities: Panel Discussion

Gerald E. Arnold of the Philadelphia Water Department reports on Philadelphia's water system, one of the oldest large water systems in the United States. The first part of the system was built in 1799, with wooden mains. Beginning in 1819, cast‐iron pipe was laid, and by 1850 all of the wooden mains had been abandoned. The more than 3,000 mi of pipe within the city limits varies in age from a few months to more than 130 years. Main breaks occur frequently in a system of this size and age, and usually occur at a point where the metal has been weakened by corrosion or some other cause, but the actual breaking of the metal occurs as a result of some unusual external force such as temperature changes, shifting ground, foreign objects, or traffic impact. Edward J. Clark of New York City's Bureau of Water Supply reports on the New York water system, where many water main breaks have been caused by settling of the main over short stretches. This causes the pipe to act as a beam, for which it is not designed, and results in fractures or loose joints. A substantial number of breaks in New York have been caused by unequal settlement of water mains along subway routes and the settlement of subsurface structures, such as electrical conduits or gas and steam mains, crossing the water pipe and resting on it. Clark presents the narrows siphon incident as the most difficult one to repair, where a break occured in a 36‐in. cast‐iron submarine pipeline crossing the narrows in New York Bay and supplying the Borough of Richmond with water. Gerald J. Remus reports on the Detroit Department of Water Supply where all water service contracts between Detroit and its suburban municipal customers require that installations must meet Detroit's standards in every characteristic. The establishment of these standards requires extreme care and sound engineering judgment. Equally important is the public relations job of winning acceptance and application of these standards. In addition, the annual repair and maintenance expenses, with service reliability, became major factors in the cost of water. Therefore, there is a twofold purpose in studying water transmission and distribution systems: to control costs and reliability, and to guide the development of an ever enlarging, reliable, and efficient water system, involving many units of government. Lastly, Howard W. Niemeyer of the Indianapolis Water Company reports that more than half of all the failures that have occurred in pipe and joints in the Indianapolis system over the past 10 years can be directly associated with the use of sulfur compound as a jointing material. Experience has also indicated that centrifugally cast pipe in 18‐ft lengths has not performed as well as pit‐cast pipe in 12 ft lengths, both being laid with sulfur compound joints.