The basic characteristics of the water supply system and the head characteristics of the working point are based on the premise, that is, the valve opening in the pipeline of the water supply system is not the premise, indicating the relationship curve H = f as shown in figure (q). In figure (q), the head H and flow q of the pump are at a certain speed. As can be seen from the figure, the larger the flow Q, the smaller the head h. Due to valve opening and constant pump speed, the flow rate is mainly determined by the user's water consumption. Therefore, head characteristics reflect the relationship between head h and water flow rate QN