If my pump is not working properly, what could be the problem?

In our experience, one cause could be that there is no technical fault with the pump, but rather that air is being sucked in on the suction side of the pump (suction hose) or there is some other fault. You can perform the following check yourself to see if there is a fault of this kind with the pump that is causing there to be no output. During operation, hold the end of the hose under the surface of the water (for example, in a bucket). If you repeatedly see air bubbles, it indicates a fault with the pump in the area of the suction line. Possible causes are: 1. The suction side is not vacuum-tight. The suction side must be completely air-tight as well as water-tight. 2. The suction filter is very dirty. The suction filter must be clean. 3. The check valve in the suction hose is stiff. The check valve must not be jammed.