Abstract: An aspirator unit comprises an aspirator having a hollow body around a vertical axis, the body having an outer wall ending at a planar lowermost surface orthogonal to the vertical axis and having a theoretical maximum area, and at least one notch as an indention in the planar bottom surface extending through the outer wall in a direction forming substantially a right angle with the vertical axis. A ratio of area of the actual planar bottom surface with the indention of the notch, to the theoretical maximum bottom surface without a notch is equal or greater than twenty percent.