What Are The Simple Water Filling Methods For Agricultural Centrifugal Pumps

Jan 02, 2026

Centrifugal pumps (except for self-priming pumps) must be filled with water in the pump and inlet pipe before starting, otherwise the pump will not be able to pump water. The centrifugal pump does not produce water after starting, often due to the air in the pump not being completely discharged and the water not being filled.

There are two main methods for filling water before starting a centrifugal pump: one is to use an assembled bottom valve to fill water, which is a one-way valve installed at the inlet of the inlet pipe. The disadvantage of this method is that the bottom valve has a large head loss, which affects the efficiency of the water pump device; Another method is to fill water without a bottom valve. The biggest advantage of this method is energy saving, which can save 10% to 15% compared to pumping stations with bottom valves. Below are several methods for filling centrifugal pumps for users to choose from when operating the water pump.

 

1. Artificial water filling method

For small pump stations with inlet pipe diameters less than 300mm, a bottom valve is usually installed at the inlet of the inlet pipe, and manual filling method is generally used, that is, water is filled from the dedicated filling and exhaust hole on the upper part of the pump casing through a filling funnel (or an inverted ordinary bottle with the bottom of the bottle removed). For small pump stations with inlet pipe diameters less than 300mm, a bottom valve is usually installed at the inlet of the inlet pipe, and water can also be filled into the pump from the outlet pipe of the pump (pump stations with shorter outlet pipes). Due to the fact that there is no need to purchase other water filling equipment, this water filling method is quite common in small rural pump stations at present.

 

 

For small pump stations without bottom valves or check valves and with short pipelines, the method of starting while filling water into the pump from the outlet pipe can also be used to gradually remove the air in the pump and pipeline. Generally, after a few minutes of continuous water filling, the pump can start pumping normally.

 

2. Vacuum water tank filling method

For small pump stations without bottom valves, vacuum water tank filling method can be used. A vacuum water tank is a closed type water tank welded with iron sheets, with a capacity of at least three times that of the inlet pipe. The installation position of the water tank should be as close as possible to the water pump, and the bottom height of the water tank should be slightly lower than the axis of the water pump. The height of a vacuum water tank is generally twice the diameter of the tank.

Before starting the water pump, fill the water tank with water and seal it. After the water pump is started, water enters from the vacuum box. Due to the decrease in water level in the tank, a certain vacuum is formed inside the tank. The water in the inlet tank will enter the tank through the inlet pipe under the action of atmospheric pressure, thus forming a water circulation and starting the normal operation of the water pump. This water filling method has the following advantages: low hydraulic loss, high pump station efficiency, low labor intensity of technical personnel, easy start-up, and is conducive to achieving automatic control of the water pump unit.

 

3. Jet pump filling method

When using a diesel engine to drive a water pump to pump water, the exhaust gas discharged by the diesel engine can be used to flow into a jet connected to the top of the water pump for pumping and filling, thereby removing the bottom valve of the water pump. When the water pump is started, close the valve cover connected to the handle, and exhaust gas is sprayed out from the jet nozzle to suck out the air in the pump 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 twofold: firstly, it fully utilizes the power machine; secondly, it improves the efficiency of the pump station.

 

4. Manual pump filling method

As a type of reciprocating volumetric pump, manual pumps are widely used in rural areas of China. Farmers can use their own manual pumps as vacuum pumps to fill centrifugal pumps with water, which is both convenient and economical.

The most common usage is to install a manual pump on the suction port of a centrifugal pump or near the inlet pipeline of the water pump, to extract air and introduce water, making it a tool for filling water when the centrifugal pump is turned on, thereby eliminating the bottom valve on the inlet pipeline of the water pump, reducing energy loss, and improving the efficiency of the water pump device.

 

5. Self guided water filling method

For semi submerged pump rooms (i.e. pump stations where the elevation of the inlet pipe and pump top are both below the water level of the inlet pool), water can be introduced into the pump by itself without the need for manual irrigation. The disadvantage of this pump station is that it does not fully utilize the suction capacity of the water pump, and the installation elevation of the water pump is lowered, which not only increases the excavation volume of the foundation, but also makes the operation and management inconvenient; But the advantages are also quite obvious, that is, it is easy to achieve automation of the pump station and has strong timeliness.

 

6. Self suspended water filling method

The self suspended water filling method is achieved through the principle of "water gas displacement" by utilizing the density difference between water and gas. This method can remove the bottom valve of the water pump.

Firstly, design a ventilation tank with an appropriate amount of container. The ventilation tank is usually made of plastic or thin iron sheet, and the cost is only half of that of the bottom valve. Then, place the ventilation tank at the inlet of the water pump, forming a connected body with the water pump and pipeline. At the same time, install a ventilation control valve on the ventilation channel between the ventilation tank and the water pump. When filling with water, fill the ventilation tank with water in advance, seal it with a lid, and then open the ventilation valve. After ventilation is completed, close the ventilation valve and suspend a portion of the water in the inlet pipe. Repeating this method several times will completely exhaust the air and fill the inlet pipe with water. At this point, the water pump can be started for lifting operations. Before shutting down, as long as the gate valve is closed before shutting down, the water intake will not return to its original position. Next time it starts, there will be no need to refill the water. The advantages of this water filling method are that the price of the ventilation tank is relatively low, it is easy to manufacture, the labor intensity is low, and it saves energy.

 

7. Vacuum pump filling method

For large and medium-sized pump stations with inlet pipe diameters greater than 300mm, or pump stations with high automation requirements, vacuum pumping devices are commonly used as water filling equipment. It is assembled from vacuum pumps and other equipment, and the vacuum pumps commonly used in drainage and irrigation stations are mostly water ring vacuum pumps.

An eccentric toothed impeller is installed inside the cylindrical pump casing of the water ring vacuum pump. The pump casing is filled with circulating water, and during vacuum pumping, the impeller rotates. 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. Due to the eccentric installation of the impeller inside the pump casing, the size of the space formed between the water ring and the toothed blades is different. When the impeller rotates clockwise, the space between the two blades in the right half gradually increases.

 

 

Under sealed conditions, as the volume of air increases, the pressure decreases, forming a vacuum. The air in the water pump and pipeline enters the crescent shaped suction port on the right side of the vacuum pump casing through the suction pipe and is sucked into the vacuum pump. The space between the two blades in the left half of the vacuum pump impeller gradually decreases, so the air is compressed and the pressure increases. Finally, it is discharged from the vacuum pump through the crescent shaped exhaust port on the left side of the vacuum pump casing and enters the water gas separation box to separate the circulating water that is taken out before being reused. The impeller keeps rotating, and the vacuum pump continuously sucks in and exhausts, finally filling the water pump with water.

Regarding the number of vacuum pumps, for small pump stations, when there are less than 3 units, generally 1 unit is selected, and when there are more than 4 units, generally 2 units are selected; For medium and large pump stations, it is best to choose two units, and when there are many units, one backup unit should be considered. The advantages of vacuum pump water filling are short filling time, high pump station efficiency, low labor intensity, and easy implementation of pump station automation. The disadvantage is that the investment is relatively large.

Centrifugal pump water filling is an important component of pump operation management. It is believed that with the continuous exploration of centrifugal pump water filling methods by water conservancy researchers, there will be more and more water pump water filling methods with the aim of "convenience, practicality, and efficiency", and the water filling effect will also become better and better, thus making positive contributions to the development of electromechanical drainage and irrigation industry.