Many users encounter a tricky issue when operating horizontal multistage centrifugal pumps: the motor runs normally, but no water flows out of the discharge port. The pump might have been pumping water stably just the previous day, so this sudden "shutdown" not only delays production but also easily causes panic. In fact, most such faults have clear causes and are not unprovoked "sudden incidents"—mastering basic troubleshooting methods allows for quick problem localization.
Horizontal multistage centrifugal pumps rely on negative pressure inside the pump to draw water. If the suction pipe connections are loose, the pipe wall has cracks, or the suction inlet is not fully submerged in water (the submersion depth must be at least 20 cm, depending on the equipment model), external air will continuously enter the pump body, disrupting the negative pressure balance. For example, some users, for convenience, only let the suction inlet barely touch the water surface. It seems that the pump can draw water, but in reality, air is constantly mixed in, leading to pumping failure.
The impeller is the core component for water conveyance inside the pump. Long-term conveyance of water containing sediment and impurities will cause wear to the impeller blades, reducing water conveyance efficiency. If impurities get stuck between the impeller and the pump casing, the impeller will be directly jammed and unable to rotate. A more easily overlooked issue is the motor rotation direction: if the wiring is incorrect after maintenance, the impeller will rotate in the reverse direction, resulting in the opposite water flow direction—naturally, no water can be pumped. In this case, it is necessary to adjust the motor wiring according to the rotation direction arrow marked on the pump body.
When the pump is used for the first time or after a long period of inactivity, if a large amount of air remains in the pump cavity and suction pipe, "air binding" will occur. Since air is much more compressible than water, the impeller cannot generate sufficient centrifugal force on the air when rotating, making it impossible to form effective negative pressure. The correct procedure is to open the exhaust valve before starting the pump, inject water into the pump until clear water flows out of the exhaust valve, and ensure the pump cavity is fully filled with water before starting the pump.
Each horizontal multistage centrifugal pump has a rated suction lift (usually 3-8 meters, subject to the equipment manual). If the vertical distance from the center of the pump body to the water surface exceeds the rated value, the negative pressure generated by the impeller will be insufficient to overcome gravity and draw water. For instance, some users install the pump on an excessively high platform to save space. Even if the pipes and impeller are in normal condition, no water can be pumped due to insufficient suction lift.
The bottom valve is installed at the bottom of the suction inlet and functions to prevent water backflow. If the valve core is stuck by aquatic plants or stones, or if the sealing surface is worn or aged, water will be unable to enter the pump body, or it will flow back into the water tank after entering. For example, in pumps used for farmland irrigation, the bottom valve is easily blocked by weeds. After starting the pump, water continuously flows back, and the pump can never retain water, leading to pumping failure. Regular cleaning of impurities from the bottom valve can prevent such problems.
When a horizontal multistage centrifugal pump fails to pump water, troubleshooting can be carried out in the order of "first check for air-related issues (air discharge, air leaks), then check components (impeller, bottom valve), and finally check installation (suction lift)". In most cases, the problem can be solved quickly. If the issue persists after self-troubleshooting, you can contact the technical team of Tianhong Pump Industry. We provide one-on-one equipment maintenance guidance to help you reduce downtime losses and ensure stable equipment operation.