The determination of the optimum renovation period for pipes seldom includes the cost of the water loss through leaks. This paper presents a complete cost model, which not only includes such costs, but aims to determine the influence of such costs in the whole problem. To this purpose, a case study has been prepared from figures obtained in Spanish utilities. A sensitivity analysis has been performed and a range of the variation of the optimum renovation period has been established for typical values of water production costs and average network pressure. Additionally, secondary influences have been studied.