2. Speed too low.
3. Discharge head higher than anticipated. Check friction loss in piping.
4. Suction lift too high. Suction pipe may be too small or long, causing excessive friction loss.
5. Impeller partially plugged.
6. Intake strainer or suction pipe partially plugged.
7. Wrong rotation direction.
8. Air pocket in suction line.
9. Air leaks in suction line and/or stuffing box (shaft seal).
10. Foot valve too small.
11. Suction not immersed deep enough.
12. Mechanical defects:
a) Wear rings worn.
b) Impeller damaged.
c) Packing of shaft seal damaged.