Possible causes	Recommended action
The pump is not primed.	Fill the pump and suction pipes with water before starting the pump.
Gate valve is closed or half-opened	Open the gate valve.
Rotate in the opposite direction	Follow the arrows to correct the wiring.
Rotate in low speed. (1) Wrong pole number of the motor. (2) Voltage is low.	(1) Check nameplate and replace the motor. (2) Check the power supply
Pump for 60Hz is operated in the 50Hz zone.	Check nameplate and replace the pump.
Impeller is clogged.	Remove the foreign objects from the impeller.
Pipe is clogged.	Remove the foreign objects from the pipe.
Foot valve or strainer is clogged.	Remove the foreign objects from the foot valve or strainer.
Air intrusion.	Inspect and repair the suction piping and stuffing box.
Foot valve or the end of suction piping is not submerged sufficiently.	Extend the suction piping and submerge the end part at least 2D.
Discharge pipe is leaking.	Inspect and repair
Corrosion of inpeller.	Check the liquid quality and change the material.
Impeller is worn out	Replacing impeller
Liner ring is worn out	Replacing liner ring
Significant loss in piping.	Review the plan
Suction head / Discharge head is high.	Review the plan
Liquid temperature is high or volatile liquid	Review the plan
Cavitation is being generated.	Consult an expert