Details on why the water pump is not pumping water:

A pump is a machine that converts mechanical energy into liquid energy to increase pressure and transport liquids. Pumps are widely used and common general-purpose machinery in the national economy. In addition to being used extensively in water conservancy, electric power, agriculture, and mining, they are particularly widely used in the petrochemical industry. Because many of the raw materials, semi-finished products, and finished products in chemical production are liquids with different physical properties, such as corrosiveness, solid-liquid two-phase flow, high or low temperature, etc., a large number of chemical pumps with certain characteristics are required to meet the process requirements. Technological development and product development in this area have been very active.

I. Reasons why the water pump does not pump water

1. Air in the water intake pipe and pump body

（ 1) Insufficient water was filled before the water pump was started. Sometimes it seems that the water filled has overflowed from the vent hole, but the pump shaft has not been rotated to completely exhaust the air, resulting in a small amount of air remaining in the water intake pipe or pump body.

（ 2) The horizontal section of the water intake pipe in contact with the water pump should have a downward slope of 0.5% or more in the direction opposite to the water flow, with the end connected to the water pump inlet being higher, and should not be completely horizontal. If it is tilted upwards, air will remain in the water intake pipe, reducing the vacuum in the water pipe and water pump, affecting water absorption.

（ 3) The packing of the water pump has been worn due to long-term use, or the packing is too loose, causing a large amount of water to spray out from the gap between the packing and the pump shaft bushing. As a result, external air enters the inside of the water pump through these gaps, affecting the water lifting.

（ 4) Due to long-term submersion, the pipe wall of the water intake pipe has corroded and holes have appeared. After the water pump is working, the water level continues to drop. When these holes are exposed to the water surface, air enters the water intake pipe through the holes.

（ 5) Cracks in the bends of the water intake pipe, or small gaps at the connection between the water intake pipe and the water pump, may allow air to enter the water intake pipe.

2. Low water pump speed

（ 1) Human factors. Some users, due to damage to the original motor, arbitrarily match another motor to drive it, resulting in low flow rate, low head, or even no water.

（ 2) Mechanical failure of the water pump itself. The impeller and pump shaft fastening nut is loose, or the pump shaft is deformed and bent, causing the impeller to move, directly rubbing against the pump body, or bearing damage, which may reduce the speed of the water pump.

（ 3) Poor maintenance of the power unit. The electric motor loses magnetism due to burnt windings. Changes in the number of turns, wire diameter, and wiring method of the windings during repair, or factors such as incomplete troubleshooting during repair, may also change the speed of the water pump.

3. The suction head of the water pump is too large

Some water sources are deep, and some water sources have relatively flat surrounding terrain, ignoring the allowable suction head of the water pump, resulting in less water suction or no water suction at all. It should be known that the vacuum that can be established at the suction port of a self-priming centrifugal pump is limited, and the vacuum suction head is approximately 10 meters of water column height, and the water pump cannot establish a vacuum.

Moreover, excessive vacuum easily causes the water in the pump to vaporize, which is detrimental to the operation of the water pump. Therefore, each centrifugal pump has its maximum allowable suction head, generally between 3~8.5 meters. When installing the water pump, do not simply seek convenience.

4. Excessive resistance loss in the water intake and outlet pipes

Some users have measured that although the vertical distance from the reservoir or water tower to the water surface is slightly less than the head of the water pump, the water lifting volume is still small or no water can be lifted. The reason is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipeline is too large.

The reason is often that the pipeline is too long, there are many bends in the water pipe, and the resistance loss of the water flow in the pipeline is too large. Generally A 90-degree bend has greater resistance than a 120-degree bend, and each 90-degree bend causes a head loss of about 0.5 to 1 meter, while every 20 meters of pipeline can cause a head loss of about 1 meter. In addition, some users arbitrarily change the diameter of the water pump inlet and outlet pipes, which also has a certain impact on the head.

5. Unbalanced electric rotor

Due to the violent vibration of the water pump, the electric rotor may be unbalanced, or the coupling may be poorly connected, the bearing may be worn and bent; the rotating parts may also be loose or broken; or the pipe support may not be firm enough. Adjustment, repair, reinforcement, and replacement methods can be used to deal with these problems.

Water or air leakage in the pipeline may be due to the nuts not being tightened during installation. If the leakage is not serious, cement can be applied to the leaking area, or cement paste mixed with asphalt oil can be used. For temporary repairs, wet mud or soft soap can be applied. If water leaks at the joints, the nuts can be tightened by hand. Serious water leaks must be reassembled. Overheating of the packing is often due to the packing being pressed too tightly, cooling water cannot reach the packing, or the shaft surface is damaged. Appropriate loosening of the packing and clearing of the blocked sealing pipe can be adopted. Worn packing must be replaced with new ones. Before installation, soak in engine oil, install one by one, and stagger the cuts, which can reduce water leakage. After the last packing is installed, tighten the pressure cover, and then adjust the tightness during operation.

The water pump does not suck water or drain water, and the reasons are often that the foot valve is stuck, the filter is clogged, the suction height is too high, or there is air leakage in the suction, or the direction is wrong, or the impeller passage is blocked. After checking one by one, measures such as repairing the foot valve, removing the clogging material, correcting the direction, and cleaning the impeller can be taken.

6. Severe vibration or noise of the pump body

This is due to the water pump being not firmly installed or installed too high, or the motor ball bearings are damaged, the water pump main shaft is bent, or it is not concentric or parallel with the motor main shaft. The water pump should be installed firmly or the installation height of the water pump should be lowered, the motor ball bearings should be replaced, the bent water pump main shaft should be corrected, or the relative position of the water pump and motor should be adjusted. Other factors, the foot valve cannot be opened. This is usually because the water pump has been left for too long, and the foot valve gasket is stuck, and the foot valve without a gasket may rust.

7. Influence of other factors

（ 1) The bottom valve cannot be opened. This is usually because the water pump has been left idle for too long, causing the bottom valve gasket to stick, or a bottom valve without a gasket may rust.

（ 2) The bottom valve filter screen is clogged; or the bottom valve is clogged by a layer of sediment in the water.

（ 3) The impeller is severely worn. The impeller blades have worn down due to long-term use, affecting the performance of the water pump.

（ 4) Malfunctions or blockages in the gate valve or check valve can reduce the flow rate or even prevent water from being drawn.

（ 5) Leakage in the outlet pipe will also affect the water lifting capacity.