A vacuum operated milking system (1) which is operable in a milking mode and a cleaning mode is provided with a vacuum system (8) which applies a vacuum to milking clusters (9) through a main milk pipeline (2) and a receiver (5) in which milk from the milking clusters (9) is collected. A pulsator valve (24) provides a pulsating vacuum to milk liners in the milking cluster (9) from the vacuum system (8). An accumulator (32) accumulates respective volumes of washing and rinsing water from a wash and rinse water trough (31) through a wash and rinse pipeline (30), which are accumulated in an annular holding chamber (43). During respective ones of a washing cycle and a rinsing cycle, a valve (54) applies atmospheric pressure to the volume of washing or rinsing water accumulated in the accumulator (32) which is urged with full flow characteristics through the main milk pipeline (2), the clusters (9) and a connecting pipe (10) for cleaning thereof. In order to minimize the maximum peak air demand on the vacuum system a control circuit (8) operates the pulsator valve (24) to apply a continuous vacuum to the milking clusters during periods when the valve (54) is operated for applying atmospheric pressure to the volume of washing or rinsing water in the accumulator (32) when the milking system (1) is operated in the cleaning mode.