A milking installation includes first and second fluid systems (S1; S2) and a coupling arrangement for connecting and disconnecting the first fluid system (S1) to and from the second fluid system (S2). In a connected state, the first and second fluid systems (S1, S2) are in fluid communication with one another, and in a disconnected state the first and second fluid systems (S1, S2) are not in fluid communication with one another. The coupling arrangement includes a common cavity (CC) configured to be alternately included in the first fluid system (S1) or in the second fluid system (S2) for through passage of fluid while the first and second fluid systems (S1, S2) are disconnected from one another. The first fluid system (S1) also has a by-pass arrangement configured to allow fluid in the first fluid system (S1) to circulate independently from the passage of fluid through the common cavity (CC) when the common cavity (CC) is included in the second fluid system (S2).