In the paper computer program “Egap” (ENO & GA Pipeline Optimizer) developed by the authors is presented. Program “Egap” implements the numerical model of hydraulic transient and cavitation phenomena based on the application of essentially nonoscillatory schemas on hyperbolic conservation laws, as well as optimization problem solution based on the application of the genetic algorithm. “Egap” can be used for pipelines in hydroelectric power plants, nuclear power plants, in oil industry, in ships, etc. It provides the capability to predict the consequences of manipulations with valves, pumps, turbines, etc. and to achieve optimal control in these operations with the goal of minimizing pressure oscillations or lengths of cavitation zones. “Egap” is developed using “Microsoft Visual C++ Developer Studio” so it is also characterized with a user-friendly Windows environment