The submersible sewage pump is a type of non-clogging pump and comes in various forms, such as the submersible type and the dry type. Currently, the most common submersible type is the WQ series submersible sewage pump, and the most common dry type sewage pumps include the W type horizontal sewage pump and the WL type vertical sewage pump. They are mainly used for transporting urban sewage, feces, or liquids containing fibers, such as paper debris and other solid particles. The temperature of the transported medium is usually not more than 80℃. Due to the presence of easily tangled or aggregated fibers in the transported medium, the flow path of this type of pump is prone to clogging. Once the pump is clogged, it will not be able to work normally and may even burn out the motor, thereby causing poor sewage discharge. This has a serious impact on urban life and environmental protection. Therefore, the anti-blocking performance and reliability are important factors in determining the quality of a sewage pump. Like other pumps, the impeller, the water pressure chamber, are the two core components of a sewage pump. The performance of these two components determines the performance of the pump. The anti-blocking performance, efficiency, and cavitation performance of the sewage pump, as well as the anti-abrasion performance, are mainly guaranteed by the impeller and the water pressure chamber. 

1. Impeller structure type: The structure of the impeller is divided into four major categories: blade type (open type and closed type), swirl type, flow channel type, (including single flow channel and double flow channel) spiral centrifugal type. Open and semi-open impellers are easy to manufacture and can be easily cleaned and repaired when the impeller is clogged. However, during long-term operation, under the abrasive effect of particles, the gap between the blades and the inner wall of the water chamber will increase, thereby reducing the efficiency. Moreover, the increase in the gap will disrupt the pressure difference distribution on the blades. Not only will a large amount of vortex loss occur, but the axial force of the pump will also increase. At the same time, due to the increase in the gap, the stability of the liquid flow state in the flow channel is disrupted, causing the pump to vibrate. This type of impeller is not suitable for transporting media containing large particles and long fibers. In terms of performance, this type of impeller has low efficiency, with the maximum efficiency being approximately 92% of that of a common closed-type impeller. The head curve is relatively flat. 

2. Spiral Impeller: For pumps equipped with this type of impeller, since part or all of the impeller is separated from the flow channel of the water pressure chamber, there is no clogging problem. It has good flow performance, strong ability to pass through particles and long fibers. Particles flow in the water pressure chamber is driven by the vortex generated by the rotation of the impeller. Suspended particles themselves do not generate energy; they only exchange energy with the liquid in the flow channel. During the flow process, suspended particles or long fibers do not come into contact with the blades, and the blades suffer less wear. There is no situation where the gap is enlarged due to erosion. In the long-term operation, it will not cause a serious decline in efficiency. Pumps with this type of impeller are suitable for media containing large particles and long fibers. In terms of performance, this impeller has a lower efficiency, which is only about 70% of that of a common closed impeller. The head curve is relatively flat. 

3. Closed impeller: This type of impeller has a relatively high normal efficiency. Moreover, it maintains a relatively stable performance during long-term operation. The pumps equipped with this type of impeller have less axial force, and additional blades can be installed on the front and rear cover plates. The auxiliary blades on the front cover plate can reduce the vortex loss at the impeller inlet and the wear of the sealing ring caused by particles. The auxiliary blades on the rear cover plate not only balance the axial force but also prevent suspended particles from entering the mechanical seal chamber, providing protection for the mechanical seal. However, this type of impeller has poor resistance to blockage and is prone to entanglement. It is not suitable for wastewater media containing large particles (long fibers) or other untreated substances. 

4. Flow channel type impeller: This type of impeller is a bladeless impeller, and the flow channel is a curved passage from the inlet to the outlet. Therefore, it is suitable for media containing large particles and long fibers. It has good anti-blocking performance. In terms of performance, this type of impeller has a high efficiency similar to that of ordinary closed impellers, but the pump's head curve of this type of impeller drops more steeply. The power curve is relatively stable, and it is less likely to cause excessive power problems. However, the cavitation performance of this type of impeller is not as good as that of ordinary closed impellers, and it is particularly suitable for pumps with pressurized inlet. 

5. Spiral centrifugal impeller: The blades of this type of impeller are twisted spiral blades, extending axially from the suction port on the conical hub body. This type of impeller has the functions of both a volumetric pump and a centrifugal pump. When suspended particles flow through the blades, they do not collide with any part inside the pump, thus having good integrity. It causes little damage to the transported material. Due to the propelling effect of the spiral, the passage of suspended particles is strong, so pumps with this type of impeller are suitable for transporting media containing large particles and long fibers, as well as high-concentration media. In situations where strict requirements are imposed on the damage to the transported medium, they have distinct characteristics. 

In terms of performance, this pump has a steeply declining head curve and a relatively flat power curve. 

The most common type of water chamber used in sewage pumps is the volute. In in-line submersible pumps, radial guide vanes or channel-type guide vanes are more commonly selected. There are three types of volutes: helical, annular, and intermediate. Helical volutes are basically not used in sewage pumps. The annular water chamber is more frequently adopted in small sewage pumps due to its simple structure and convenient manufacturing. However, with the emergence of the intermediate type (semi-helical) water chamber, the application scope of the annular water chamber has gradually decreased. This is because the intermediate type water chamber combines the high efficiency of a helical design and the high permeability of an annular water chamber.