Pipelines in water supply systems age slower or faster in a number of
ways and for different reasons. A description is given of the causes o
f deterioration in conditions which finally lead to degradation and su
dden failures of system elements. The life-span or service life of a p
ipeline can be extended by maintenance and repair measures and, after
reconstruction and replacement, it starts practically from new. A prob
ability model is proposed in which the life-span of a pipeline is cons
idered as a random variable. In this model, pipelines exhibit expectan
cy values for their (residual) life-span, survival and renewal probabi
lities which are mathematically interrelated. An application within th
e framework of a cohort survival model for pipeline types shows, for 1
0 European water supply systems, what future renewal rates result from
the current system stock of the particular water utility with more or
less optimistic assumptions of life expectancy of pipe types.