Abstract: A study carried out to evaluate some alternative approaches that are used to calculate hydraulic transients in complex pipelines.It is demonstrated that these methods are not satisfactory in regard to numerical accuracy, computation time, application flexibility and simplicity.A new method is presented which allows to use variable time-steps for pipeline sections and to compute value at interior nodes in advance of boundary nodes in terms of computation order, and value at boundary nodes in advance of interior nodes in terms of time. The usage of parabolic interpolation by time in this method is described.