| Possible causes | Recommended action |
| Bearing is damaged. | Replacing bearing |
| No-discharge operation for a long time. | Stop no-discharge operation. |
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
Electric motor does not work well with noise.
Water comes out at first, but it doesn't come out soon.