(l) The sewage pump lift pump can't deliver water or feed water: there is air in the pipeline and pump body. Before starting the sewage pump, it was not filled with enough water. Sometimes it seems that the injected water has overflowed from the vent hole, but the pump shaft does not rotate to completely discharge air, resulting in a little air remaining in the water inlet pipe or the pump body. The horizontal section of the water inlet pipe in contact with the water pump should have a descending slope of more than 0.5% against the water flow direction, and the end connected with the inlet of the water pump should be the highest and not completely horizontal; If it inclines upward, air will remain in the water inlet pipe, which will reduce the vacuum degree in the water pipe and pump and absorb water in N direction. Due to long-term use, the packing of the water pump has been worn or pressed too loosely, resulting in a large amount of water spraying from the gap between the packing and the shaft sleeve of the pump. As a result, outside air enters the pump from these gaps, which affects the water lifting. Due to long-term potential underwater, there are holes in the wall of the water inlet pipe, and the water level of the pump keeps falling after working. When these holes are exposed to water, air enters the water inlet pipe from the water inlet company. Cracks appear at the elbow of the water inlet pipe, and tiny gaps appear at the joint between the water inlet pipe and the water pump, which may make air enter the water inlet pipe.

(2) The rotating speed of sewage lifting pump is too low. Man-made factors: some users randomly matched another motor to drive the water pump due to the damage of the original motor, resulting in small pump flow, low lift and even no water supply. Mechanical failure of the pump itself: loose fastening nut between the impeller and the pump shaft or deformation and bending of the pump shaft may cause the impeller to move, directly rub the pump body or damage the bearing, thus reducing the speed of the pump. Poor maintenance of power machine: the motor loses magnetism due to winding burning, and the change of winding turns, wire diameter and connection mode during maintenance, or the failure during maintenance is not completely eliminated, will also change the pump speed.

(3) The suction range is too large. Some water sources are deep, and some water sources are flat around, ignoring the allowable water absorption range of the pump, which will cause little or no water absorption. The vacuum degree that can be established at the suction port of the pump is limited. The suction range of absolute vacuum is about 10 m water column, but it is impossible for the pump to establish absolute vacuum. Excessive vacuum is easy to vaporize the water in the pump, which is not good for the pump. Therefore, each centrifugal pump has its maximum allowable suction range, which is generally between 3 and 8.5m. It is only convenient and simple to install the water pump.

(4) The resistance loss of inlet and outlet pipes is too large. Sometimes the vertical distance from the reservoir or water tower to the water surface of the water source is slightly smaller than the pump head, but it still leads to less water. The reason is that the pipeline is too long, the water pipe bends a lot, and the resistance loss of water flow in the pipeline is too great. Under normal circumstances, 90

(5) The influence of other factors. Bottom valve can't be opened: usually, the water pump has been put on hold for too long, and the gasket of the bottom valve is stuck, and the bottom valve without gasket may rust. The filter screen of the bottom valve is blocked, or the filter screen is blocked in the silt layer in the diving of the bottom valve. Impeller wear is serious: the impeller blades wear after long-term use, which affects the performance of the pump. The failure or blockage of gate valve or check valve will reduce the flow and even prevent the pump from pumping water. The leakage of the outlet pipeline will also affect the extraction of water,