Abstract: A milking system in which milk is drawn during milking into a vacuumized milk collector and let off through a downstream sluice is rinsed automatically with air being admitted periodically into a preliminary-run line of an automatic rinser to improve rinsing. A preliminary-run container is positioned between the sluice and a preliminary-run line of the automatic rinser and communicates through connecting lines with the preliminary-run line and the sanitary trap and through a run-off and a connecting line with the sluice. Valves are mounted in the run-off and open the line to the sluice only when there is liquid in the preliminary-run container and a vacuum in the sluice. This prevents atmospheric air from flowing from the preliminary-run line into the sluice or air from being drawn out of the sluice when there is atmospheric pressure in the sluice.