The operation of the GERTEC hose pumps is based on the principle of peristaltic delivery, i.e. the ability of the pump hose to restore its initial shape after each crush. While the rotating pressure roller is crushing the hose pump by running over it, the suction side is disconnected from the delivery side. The rising of the hose pump after each crush creates a cavity, which causes a suctioning of the delivery medium. Simultaneously, the delivery medium is squeezed out of hose pump on the pressure side.