1. There is a crack at the elbow of the sewage pump inlet pipe, and a slight gap occurs at the connection between the inlet pipe and the water pump, which may cause air to enter the inlet pipe.
2. The sewage pump is not filled with enough water before starting. Sometimes it seems that the water has overflowed from the venting hole, but the air is not completely discharged from the pump shaft so that a little air remains in the inlet pipe or the pump body. The pump speed is too low.
3. The packing of the sewage pump has been worn out due to long-term use or the packing is too loose, causing a large amount of water to be ejected from the gap between the packing and the pump shaft bushing. As a result, external air enters the inside of the pump from these gaps, which affect water lifting.
4. The horizontal section of the inlet pipe that the sewage pump connects should use a downward slope of 0.5% or more, and the end of the water pump inlet should be high, not completely horizontal. If it is lifted up, air will remain in the inlet pipe, which will reduce the vacuum in the water pipe and the water pump, and affect the water absorption.
5. Because the inlet pipe is exposed to water for a long time, the pipe wall will be corroded and occurs the holes. After the pump works, the water surface continuously drops. When these holes are exposed to the water surface, the air enters the water inlet pipe from the hole.
6. Human factors. Some users are randomly equipped with another motor to drive the original motor, resulting in low flow, low head or even no water.
7. Mechanical failure of the sewage pump itself. The impeller and the pump shaft fastening nut are loose or the pump shaft is deformed and bent, causing the impeller to move, directly rubbing against the pump body, or the bearing is damaged, which may reduce the rotation speed of the pump.
8. The impeller of the sewage pump is seriously worn. The impeller blades wear out over a long period of time, which affects the performance of the pump.
9. The filter screen of the bottom valve of the sewage pump is blocked, or the filter is blocked in the sludge layer of the bottom water.
10. The bottom valve of the sewage pump cannot be opened. Usually, because the pump is left aside too long, the bottom valve gasket is stuck, and the bottom valve without the gasket may rust.
11. The gate valve can be faulty or blocked by the check valve, which will reduce the flow or even cannot pump water.
12. Leakage of the outlet pipe of the sewage pump will also affect the amount of water. Power machine maintenance does not work. The motor is field-loss due to the burning of the windings. The number of winding turns, the wire diameter, the wiring method change during maintenance, or the failure to completely eliminate the fault during maintenance will also cause the pump speed to change.
The suction head is too large, some water source is deeper, and some has a flatter outer surface, which ignores the allowable suction head of the water pump, thus resulting in less water absorption or no water absorption at all. It is important to know that the vacuum that can be established at the suction port of the pump is limited. The absolute vacuum suction is about 10 meters high, and the pump cannot establish an absolute vacuum. Moreover, the degree of vacuum is too large, which makes it easy to vaporize the water in the pump, which is detrimental to the operation of the pump. Therefore, each centrifugal pump has a large allowable suction head, generally between 3-8.5 meters. When installing the water pump, it must not be simple and simple.
The resistance loss in the water inlet and outlet pipes is too large. Some users have measured that although the vertical distance between the reservoir or the water tower to the water source is slightly smaller than the pump head, the water lifting amount is small or the water is not lifted. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the water flow is excessively lost in the pipeline. Under normal circumstances, the 90-degree bend is more resistant than the 120-degree bend. The head of each 90-degree bend is about 0.5-1 meters. The resistance of each 20-meter pipeline can cause the head loss to be about 1 meter. In addition, some users also pay no attention to the diameter of the pipe inlet and outlet pipes, which also has a certain impact on the head.