Before starting the centrifugal pump, it is necessary to fill it with water to expel the air inside the pump casing. According to the working principle of a centrifugal pump, when the impeller rotates, water is thrown towards the outer edge of the impeller by centrifugal force, creating a vacuum at the center of the impeller. Water is sucked in, forming a continuous working process of the water pump. If the pump body is not filled with water but with air when started, the centrifugal force generated by the air will be much smaller than that of water when the impeller rotates at the same speed, as the density of air is much lower than that of water. This will gather at the center of the impeller, preventing sufficient vacuum from forming at the center of the impeller, hindering the suction of water, and affecting the formation of the continuous working process of the water pump. Therefore, before starting the centrifugal pump, it must first be filled with water and the air inside the pump body must be drained in order to maintain the normal operation of the water pump.

Before starting a centrifugal pump, the pump and inlet pipe must be filled with water, 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.

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.

There are two main methods for filling water before starting: 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.