Threshold Break Rate for Pipeline Replacement in Water Distribution Systems

A comprehensive review of pipe replacement analyses is presented, from which an economically sustainable threshold break rate for replacement of pipelines in deteriorating water distribution systems is derived that yields some of the previously available replacement criteria under weaker restrictions. Relations of equivalence are established between the threshold break rate and both the rate of occurrence of failure (ROCOF) and the hazard rate functions. These statistical functions are used to predict break rates for a system. Optimal replacement times are obtained by equating the threshold break rate and the assessed (predicted) break rate from the ROCOF and the hazard rate functions. Design charts to determine the optimal threshold break rate as a function of pipe diameter and discount rate are also given, as well as numerical examples illustrating the developed theory.