This paper describes the application of the successive-approximation (i.e. Hardy Cross) method for determining the optimal hydraulic solution of a gas-pipeline network. The latter takes the form of a ring-like and branched structure, with known node gas consumptions and flow velocities below certain maximum specified values. The optimization was carried out by iteration of the values of the network parameters (e.g. alteration of the pipe diameter) and then repeating the computation procedure.