A sanitary backwashing system for an automatic milking machine having a milking unit and a source of vacuum, the system including a valve having a first port connected to the milking unit and a pair of second ports alternately connected to the first port, one of the second ports being connected to the source of vacuum; and a source of sanitizing fluid under pressure connected to the other of the second ports and the valve having a first position in which the valve connects the milking unit to the source of vacuum while blocking off the other of the second ports and a second position in which the valve connects the milking unit to the source of sanitizing fluid while blocking off the source of vacuum.