The centrifugal pump (except the self-priming pump) must be filled with water before starting, otherwise, the pump will not be able to lift water. The centrifugal pump does not produce water after starting, which is often caused by the fact that the pump is not filled with water before the pump is started, and the air in the pump is not expelled.

There are two main methods of filling water before starting:
One is to use the assembled bottom valve to fill the water. The bottom valve is a one-way valve and is installed at the inlet of the water inlet pipe. The disadvantage of this method is that the head loss of the bottom valve is large, which affects the installation efficiency of the pump;
The other is water filling without the bottom valve. The biggest advantage of this method is energy saving.

Here are some water filling methods for centrifugal pumps for users to choose when running the pump.

self-priming water filling
For the semi-submerged pump house (the pump station where the water inlet pipe and the pump top are both below the water level of the water inlet pool), the water can be introduced into the pump by itself without manual irrigation. The disadvantage of this pumping station is that the water absorption capacity of the pump is not fully utilized, and the installation elevation of the pump is reduced, which not only increases the amount of foundation excavation but also makes the operation and management more inconvenient; but the advantages are also obvious, that is, it is easy to realize the pumping station. Automatic and time-sensitive.

Manual water filling
For small pumping stations with an inlet pipe diameter less than 300mm, the inlet of the inlet pipe is usually equipped with a bottom valve, which is generally used to fill the water manually, i.e. from the special water filling vent at the upper part of the pump shell by the water filling funnel, and also from the outlet of the pump (pumping stations with shorter outlet pipe) to fill the pump with water.

For small pumping stations without the bottom valve, check valve, and short pipeline, you can also use the method of starting while filling water from the outlet to the pump, so as to gradually bring out the air in the pump and pipeline, generally after a few minutes of continuous water filling, the pump can work normally pumping water

Vacuum tank filling
For small pumping stations without the bottom valve, the vacuum water tank filling method can be used. The vacuum water tank is a closed water tank welded with iron sheets, and its volume is at least 3 times the volume of the water inlet pipe. The installation position of the water tank should be as close to the water pump as possible, and the bottom height of the water tank should also be slightly lower than the axis of the water pump. The height of the vacuum tank is generally 2 times the diameter of the tank.

Before starting the pump, fill the tank with water to seal it. After the water pump is started, the water pump enters the water from the vacuum tank. Due to the drop of the water level in the water tank, a certain vacuum is formed in the water tank. The pump starts to run normally.

Jet pump water filling
When the diesel engine is used to drive the water pump to pump water, the exhaust gas discharged by the diesel engine can be used to pass into the jet connected to the top of the water pump to pump air and fill the water, thereby removing the bottom valve of the water pump. When the water pump is started, the valve cover connected to the handle is closed, the exhaust gas is ejected from the ejector, and the air in the pump is sucked out through the connecting pipe. After filling the water, open the valve cover and close the control valve. The advantages of this water filling method are that the power machine is fully utilized, and the efficiency of the pumping station is improved.

Self-suspension water filling
The self-suspension water filling method is realized by the principle of "water-gas replacement" by using the bulk density difference between water and gas. This method can remove the bottom valve of the water pump. First of all, design a ventilation tank with an appropriate amount of containers. The ventilation tank is generally made of plastic or can be a thin iron piece, and the cost is only half of the bottom valve. Then, place the ventilation tank at the water inlet of the water pump to form a connection with the water pump and pipeline. At the same time, a ventilation control valve is installed on the ventilation channel between the ventilation tank and the water pump. When filling with water, fill the ventilation tank with water in advance, then seal it with a lid, and then open the ventilation valve. After the ventilation is completed, close the ventilation valve, and part of the diversion water will be suspended in the water inlet pipe. Repeat this method several times, the air will be completely exhausted, and the water inlet pipe will be filled with water. At this point, the water pump can be started for pumping. Before shutting down, as long as the gate valve is closed first and then shut down, the water diversion will not sit back. The next time you startup, you don't need to water it again. The advantages of this water filling method are that the price of the ventilation tank is lower, the manufacture is easy, the labor intensity is low, and energy is saved

Vacuum pump water filling
For large and medium-sized pumping stations with a water inlet pipe diameter greater than 300mm, or pumping stations with high automation requirements, a vacuum pumping device is a commonly used water-filling equipment. It is assembled by the vacuum pump and other equipment. Most of the vacuum pumps often used in irrigation and drainage stations are water ring vacuum pumps.

The water ring vacuum pump has an eccentric tooth-shaped impeller installed in the cylindrical pump casing. When the pump casing is filled with circulating water, the impeller rotates and under the action of centrifugal force, the circulating water in the pump casing is thrown around the impeller, forming a rotating water ring on the inner wall of the pump casing. Because the impeller is installed eccentrically in the pump casing, the space formed between the water ring and the tooth-shaped vane is different in size. When the impeller rotates clockwise, the space between the two vanes in the right half of the impeller increases gradually, and under the closed condition, as the volume of air increases, the pressure decreases, and a vacuum is formed. Finally, the air is discharged from the vacuum pump through the crescent-shaped exhaust port on the left side of the pump casing and enters the water-gas separation tank, so that the circulating water is separated and then reused. The impeller keeps rotating, the vacuum pump keeps sucking and exhausting, and finally, the pump is filled with water.

Manual pump filling method
As a kind of reciprocating positive displacement pump, it is convenient and economical to fill the centrifugal pump with water. The most common usage is: to install the manual pump on the suction hole of the centrifugal pump or on the water inlet pipeline near the water pump and carry out air suction and water diversion, making it a tool for filling water when the centrifugal pump is turned on, thus saving the need for the water inlet pipeline of the pump. The bottom valve reduces the energy loss and improves the efficiency of the pump unit