(1) The water pump is not filled with enough water before starting. Sometimes it seems that the water filled has overflowed from the air vent, but the pump shaft is not rotated to allow the air to be completely discharged, resulting in a little air remaining in the water inlet pipe or pump body.
(2) The horizontal section of the water inlet pipe that is in contact with the water pump should have a descending slope of more than 0.5% in the direction of the water flow, and the end connected to the inlet of the water pump should be the highest, not completely horizontal. If it is tilted upwards, air will remain in the water inlet pipe, which will reduce the vacuum degree in the water pipe and the water pump and affect the water absorption.
(3) The packing of the water 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 sleeve. As a result, the external air enters the inside of the pump from these gaps. Affects water extraction.
(4) Due to the long-term submersion of the water inlet pipe, there are holes in the pipe wall due to corrosion. After the pump works, the water surface continues to drop. When these holes are exposed to the water surface, the air enters the civilian water inlet pipe from the holes.
(5) Cracks appear at the elbow of the water inlet pipe, and there is a tiny gap at the connection between the water inlet pipe and the water pump, which may allow air to enter the water inlet pipe.
The pump speed is too low
(1) Human factors. Some users randomly add another motor to drive because the original motor is damaged, resulting in the consequences of small flow, low head or even no water supply.
(2) Mechanical failure of the pump itself. The tightening nut between the impeller and the pump shaft is loose or the pump shaft is deformed and bent, causing the impeller to move more, directly rubbing against the pump body, or damage to the bearing, which may reduce the speed of the pump.
(3) The maintenance of the power engine fails. The motor is demagnetized due to the burning of the winding, the change of the number of turns of the winding, the wire diameter, and the wiring method during the maintenance, or the factors that the fault is not completely eliminated during the maintenance will also change the speed of the pump.
Too much suction
Some water sources are deep and the surrounding terrain of some water sources is relatively flat, and the allowable suction lift of the pump is ignored, resulting in the result that the water absorbs less or cannot absorb water at all. It should be known that the vacuum degree that can be established at the suction port of the pump is limited. The suction lift of absolute vacuum is about 10 meters high, and it is impossible for the pump to establish an absolute vacuum. And if the vacuum is too large, it 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 lift, which is generally between 3-8.5 meters. When installing the water pump, it must not only be convenient and simple.
The resistance loss of the water flow in and out of the water pipe is too large
Some users have measured that although the vertical distance from the reservoir or water tower to the water surface of the water source is slightly smaller than the pump head, the amount of water lifted is still small or cannot be lifted. The reason is often that the pipeline is too long, the water pipeline has many bends, and the resistance loss of the water flow in the pipeline is too large. The reason is often that the pipeline is too long, the water pipeline has many bends, and the resistance loss of the water flow in the pipeline is too large. Under normal circumstances, the resistance of a 90-degree elbow is larger than that of a 120-degree elbow, and the lift of each 90-degree elbow will lose about 0.5-1 meters, and the resistance of each 20-meter pipeline can cause the lift to lose about 1 meter. In addition, some users also choose the diameter of the pump inlet and outlet pipes, which also has a certain impact on the lift.
Influence of other factors
(1) The bottom valve cannot be opened. Usually because the water pump is left for too long, the bottom valve gasket is stuck, and the bottom valve without gasket may rust.
(2) The filter screen of the bottom valve is blocked; or the filter screen is blocked in the sludge layer in the latent water of the bottom valve.
(3) The impeller is seriously worn. The impeller blades are worn out after long-term use, which affects the performance of the pump.
(4) The failure or blockage of the check valve of the gate valve will cause the flow to decrease or even to not be able to pump water.
(5) The leakage of the outlet pipe will also affect the amount of water lifted.
