Developed countries have opted to transport drinking water to households via long networks of pipes, which are expensive to install and maintain. Their management is therefore an important issue for water utilities. Water asset management is a complex multicriteria problem since managers have lots of different objectives. This article focuses on “long term” strategic methods. Particularly it is centered on a new way to estimate the “number of future pipe breaks in the long term at the scale of the water utility territory”. This paper first estimate prospective pipe age distribution at a given network section location over time. Then equations of deterioration process of pipe sections are build-up. Finally both models are mixed. Our case study is eauservice Lausanne, the third water utility of Switzerland. The proposed approach is different from existing “long-term” models because it is based on actual historical survival function.