The performance indicators defined in Guidelines for the management and assessment of a drinking water supply service, which was published in 2005 by the JWWA Technical Committee in Japan, are often applied to compare ones of different water supply utilities. On the other hand, the PIs are useful to estimate results of a new project which a water supply utility will plan.
This paper shows results of the evaluation of an imaginary project which the authors intend to promote concerning replacement of old pipelines using the numerical model of PIs on condition that any factors of the existing water supply utility are not changeable. The authors can estimate numerical variation of the other PIs caused by pipeline replacement, which are water charge, leakage ratio, pipeline burst ratio, redundancy of water resource and so on. This study shows that PIs make it easy to evaluate a new project.