Pump does not prime; pressure gauge and vacuum gauge needles fluctuate violently                

1.Insufficient priming water 

2.Air leakage at pipe or instrument connections

3. Suction lift too high 

1. Check if foot valve leaks; refill with sufficient priming water

2.Tighten leaking points

3.Reduce suction height 

Pump does not prime; vacuum gauge indicates high vacuum

1. Foot valve not opened or clogged

2.Excessive resistance in suction line

3.Strainer clogged  

1.Inspect foot valve 

2.Replace suction line 

3.Clean strainer 

Pressure gauge shows pressure but no water is discharged 

1.Excessive resistance in discharge line 

2.Incorrect rotation direction 

3.Discharge valve not opened 

4.Impeller clogged  

1.Inspect or shorten discharge pipe 

2.Check motor; interchange two phases 

3.Open discharge valve 

4.Remove debris from impeller 

Design flow rate not achieved 

1.Air ingress 

2. Insufficient submergence due to lowered water level 

3. Foreign matter clogging impeller 

4.Severe wear of rotating parts 

1.Locate and eliminate air leakage 

2.Extend suction pipe; increase submergence depth

3.Disassemble and remove foreign matter 

4.Replace seal ring 

Excessive power consumption

1.Packing gland too tight and overheating 

2. Flow rate too high 

3.Rubbing between rotating element and casing 

4.Pump bearing worn 

5.Pump shaft bent 

1.Loosen appropriately 

2.Partially close gate valve

3.Trim or repair 

4.Replace bearing 

5.Replace or straighten shaft  

Excessive pump vibration 

1.Partial clogging of impeller 

2. Impeller damaged 

3.Flow rate too low 

4.Pump shaft and motor shaft misaligned 

5.Bearing damaged 

6.Air ingress causing cavitation                                                          

1.Disassemble and remove foreign matter 

2.Replace impeller

3.Slightly open discharge valve

4.Align shafts by dial gauge 

5.Replace bearing

6.Change suction position; improve suction line