A method for operating a washing machine

The present invention relates to a method for operating a washing machine (10) comprising a washing tub (24) containing a laundry drum (26), said method comprises the steps of: - detecting a liquid level (44) in said washing tub (24) and/or in a draining region thereof while said laundry drum (26) is rotating at a first speed, - comparing the detected liquid level (44) with an upper threshold value (48), wherein the excess of said upper threshold value (48) by the liquid level (44) while the laundry drum (26) rotates at a rotation speed equal or higher than said first speed generates a closed liquid ring at circumferential walls of the laundry drum (26), and - if the detected liquid level (44) exceeds the upper threshold value (48), then reducing the rotational speed of the laundry drum (26) below said first speed and performing a foam- detecting procedure for detecting the amount and/or presence of foam inside the washing tub (24) and/or in the draining region thereof. Further, the present invention relates to a corresponding washing machine (10). Moreover, the present invention relates to a computer program product for performing the method for operating a washing machine (10).