What Are The Main Reasons For The Leakage Of Sewage Submersible Pumps

Jan 12, 2026

Submersible sewage pumps are mainly used for environmental protection services, characterized by high efficiency, no blockage, easy use, and no need to build pump rooms. Submersible sewage pumps are widely used in municipal construction, factories and mines, hotels, sewage treatment projects, etc. In the long-term use of sewage submersible pumps, it is inevitable to encounter some problems. So how should users deal with these problems in time?
Mechanical seals are the main cause of leakage in sewage submersible pumps, but mechanical seals themselves are precision components with high requirements for design, machining, and assembly quality. When using mechanical seals, various factors related to the use of mechanical seals should be analyzed to ensure that they are suitable for the technical requirements and medium requirements of various pumps and have sufficient lubrication conditions, so as to ensure the long-term reliable operation of sewage submersible pump seals.

 

Mechanical seal, also known as end face seal, has a pair of end faces perpendicular to the axis of rotation. Under the action of fluid pressure and compensating mechanical external elasticity, these end faces rely on the cooperation of auxiliary seals to maintain contact with the other end and slide relative to each other, thereby preventing fluid leakage.

Common leakage phenomena

The proportion of mechanical seal leakage accounts for more than 50% of all repaired sewage submersible pumps. The operation of mechanical seals directly affects the normal operation of sewage submersible pumps. The summary and analysis are as follows.
1. Periodic leakage
(1) The axial displacement of the rotor of the sewage submersible pump is large, and the interference between the auxiliary seal and the shaft is large. The dynamic ring cannot move flexibly on the shaft. After the sewage submersible pump is overturned and the dynamic and static rings wear out, no compensation displacement can be obtained.
Countermeasure: When assembling mechanical seals, the axial displacement of the shaft should be less than 0.1mm, and the interference fit between the auxiliary seal and the shaft should be moderate. While ensuring radial sealing, the dynamic ring should be able to move flexibly on the shaft after assembly (by pressing the dynamic ring against the spring and allowing it to bounce back freely).

 

(2) Insufficient lubricating oil on the sealing surface can cause dry friction or fraying of the sealing end face.
Countermeasure: The height of the lubricating oil level in the oil chamber should be increased to be higher than the sealing surface of the dynamic and static rings.
(3) Periodic vibration of the rotor. The reason is that the stator is not aligned with the upper and lower end covers or the impeller and main shaft are unbalanced, resulting in cavitation or bearing damage (wear), which can shorten the sealing life of the sewage submersible pump and cause leakage.
Countermeasure: Sewage submersible pumps can correct the above problems according to maintenance standards.