We design a leak detection, size estimation and localization algorithm for a branched pipe system, requiring flow and pressure measurements to be taken at the inlet and outlet boundaries, only. By showing that the pipe system model can be mapped into a system of coupled, linear hyperbolic PDEs (partial differential equations), with the parametric uncertainties caused by the leak appearing in a particular way, established methods can be applied to obtain state and parameter estimates. Analyzing the structure of the parametric uncertainties that appear in the obtained adaptive observer canonical form, we prove that total leak size can be estimated regardless of how leaks are distributed in the pipe network. Moreover, any number of point leaks can be located, provided they occur sufficiently separated in time.