Abstract-A district heating system is comprised of three parts: a heating production plant, an exchanger unit, and a pipe network of the district heating. In this paper, we will analyze the flow of the fluid through technical pipes, which will be considered as one-dimensional. The optimal velocity of the flow and its analysis will be determined according to the size of mechanical power losses between 0 Pa/m up to over 200 Pa/m, based on the dependence of the velocity of the flow v=f (,l,d,h f ), according to which we have managed to do the calculation for the approved model with pipe length from l=1 m. The pipe used for this study is from PREMANT (Pre-insulated Steel Pipe System German Pipe Brugg) manufacturer. In the paper, we will conduct an analysis to determine the optimal velocity of the flow of the fluid, for the approved model, by using the equations related to energy losses.