Maintaining Carrying Capacity of Cast Iron Main by Introduction of Chloramines

Abstract

After varying periods of time, depending upon the aggressiveness of the water and the perfection of the protective coating, these cast iron mains will be found internally corroded and tuberculated to such an extent as to interfere with their carrying capacity, thus necessitating recourse to some method for removing the accumulations which, by their presence, interfere with the flow of water. Many hypotheses have been advanced to account for and explain pipe corrosion and tuberculation. Previous to 1931, these different hypotheses of corrosion were classified into three types. Self corrosion was the result accompanying the contact of metals with water and free oxygen. Galvanic corrosion caused the results obtained when two different metals in contact at one point are immersed in water. Brass to iron fittings often lead to this form of corrosion. In some cases, free carbon in the graphite form, in the cast iron will yield the same results. Electrolysis corrosion covered the effect produced by stray currents from street railway systems, etc. In 1931, Messrs. H. G. Reddick and S. L. Linderman injected a new, and in some respects, startling theory to account for tuberculation the biological, or bacterial theory. In their paper presented at the 1931 meeting of the New England Water Works Association at Boston, these authors developed the thesis that the nodules and tubercles from old cast iron pipe possessed many characteristics in common, in composition, magnetic properties and structure.