A software application implementable on a computer system is used to create a model of a hydraulic system to perform calculations. The user visually constructs a two-dimensional (2-D) connectivity model in the computer system. The 2-D connectivity model has a plurality of node points defined at various elements (sources, outlets, equipment, and junctions) of the hydraulic system and has segments interconnecting the node points. The user visually constructs a three-dimensional (3-D) segment model for each segment so that each segment model has the 3-D layout of the piping and the fittings for the segment. A 3-D system model of the entire hydraulic system is visually created in the computer system by combining the 3-D segment models. The software application performs calculations using the 3-D system model, and the 3-D system model can be visually or automatically verified to determine whether the model substantially corresponds to the 3-D layout of the hydraulic system, and has been laid out without errors.