| Possible causes | Recommended action |
| Electric motor failure. | Repair electric motor. |
| Power supply problem. | Inspect and repair |
| Rotating part contacted, rusted or seized. | Turn it by hand. Reassemble. Repair at a specialized factory |
| Foreign objects are get involved in to the sliding part. | Remove the foreign objects from the sliding part. |
Rotating, but water does not come out. Discharge quantity is not enogh to specified capacity.
Over load (Overcurrent) occurs.
Excessive water leakage from stuffing box
Water comes out at first, but it doesn't come out soon.