A method for controlling a drainage pump configured to operate at a variable operational speed, and a drainage pump assembly so controlled. The drainage pump has a drive unit including an electrical motor and a drive shaft, and a hydraulic unit with an impeller operatively connected to the electrical motor via the drive shaft. The method includes continuously operating the drainage pump at a positive operational speed with default operation at a predetermined idle operational speed, and intermittently detecting whether the drainage pump is snoring or not snoring. The operational speed is decreased by one step when snoring is detected, and increased by one step when snoring is not detected.