There are three main performance curves for submersible sewage pumps: flow head curve, flow power curve, and flow efficiency curve.

1. Flow efficiency curve. Its curve resembles the shape of a mountain. When the flow rate is zero, the efficiency is also zero. As the flow rate increases, the efficiency gradually increases, but after reaching a certain value, the efficiency decreases. The efficiency has a value, and around the rate point, the efficiency is relatively high. This area is called the high efficiency zone.

2. Flow power curve. The shaft power increases with the flow rate. When the flow rate Q=0, the corresponding shaft power is not zero, but a certain value (about 60% of normal operation). This power is mainly consumed in mechanical losses. At this time, the water pump is filled with water. If it runs for a long time, it will cause the temperature inside the pump to continue to rise, and the pump casing and bearings will heat up. In severe cases, it may cause thermal deformation of the pump body, which is called "stagnant head". At this time, the head is high, and when the outlet valve gradually opens, the flow rate will gradually increase, and the shaft power will also slowly increase.

3. Flow head characteristic curve. It is the basic functional curve of a centrifugal pump. Centrifugal pumps with a specific speed less than 80 have the characteristics of rising and falling (protruding in the middle and bending down on both sides), known as the hump function curve. Centrifugal pumps with a specific speed between 80 and 150 have a flat functional curve. Centrifugal pumps with a specific speed of over 150 have a steep decline function curve. Generally speaking, when the flow rate is low, the head is high, and as the flow rate increases, the head gradually decreases.

The mutual variation and constraint between the performance parameters of submersible sewage pumps: Firstly, the rated speed of the pump is taken as a prerequisite. There is a certain relationship between the performance parameters of submersible sewage pumps, such as flow rate Q head H shaft power N speed n efficiency η. The relationship between their quantitative changes is represented by a curve, which is called the performance curve of the water pump.