A study of the change in pressure and flow in a pipeline that is connected to a tank (point B) having a constant water level for the entire time of the transition mode phenomenon, which occurs during the closure of the valve located at the end of the horizontal gravity of the pipeline (point A). Closing of this valve is performed in three ways - instantaneous, sudden and slow mode, the closing operation of the valve is expressed through a function of the time t and the parameter γ, characterizing the form of closing the section of this valve, γ can vary in the interval [0,7-1,5]. Variables of pressure and water flow rate at points (Q_t^A, H_t^A), (Q_t^B,H_t^B) и (Q_t^c,H_t^c ), at any instant t, respectively, to the gate valves, the tank and in the middle of the pipeline (point C), will be determined in two ways, the graphical method is the well-known Bergeron method, and the second is the analytical method of characteristics