In effective planning a new water distribution system or enlarging an existing one we need to simulate the circumstances of the system on a computer and determine the best possible solutions. On the other hand if we have an existing water distribution system we want to run it as optimally as possible - that means that the system should need as small an amount of energy as possible and still satisfy all the required needs. It is obvious that even if we have to deal with the same water distribution system we need a completely different mathematical approach to solve these two problems simulation on a computer. We developed two approaches: microscopic models and macroscopic models which were tested and gave very good results by adequately describing the circumstances in the working network, as well as in respect of computing time and energy optimization problem.