CORROSION AS A PRIMARY CAUSE OF CAST-IRON MAIN BREAKS

B in cast-iron water mains are becoming more numerous each year, and subsequent underground leakage is frequently the principal cause of unaccounted for water." Many leaks, of course, are due to accidents or physical damage to otherwise sound pipe. It has been recognized, however, by water utility personnel that the majority of the breaks occur at locations where the pipe wall has been weakened. Such weakening is the result of graphitic corrosion of cast iron and, although the actual failure may be due to stress, corrosion can be shown to be the real cause. The cost of corrosion to the water utility industry has been estimated conservatively at $150,000,000 annually." This expense, along with the nuisance of pipeline breaks, can be reduced greatly through the application of modern corrosion control methods. Similarly, corrosion control needs to be considered for all new construction. This is essential not only from an economic standpoint, but also because of the increased value of water. Water shortages make reduction of leakage imperative. This article outlines the corrosion process with emphasis on cast iron. Data are cited to show the relationship between breaks and known corrosion phenomena. Finally, recommendations for corrosion control and hence a reduction of main breaks are discussed.