A valve for connecting two flexible hoses of a milking machine to a milk line and a vacuum line, respectively, comprises a housing containing two opposite valve seats and a rotatable slide having sealing surfaces cooperating with said seats. The slide is provided with a recess for receiving a connection piece connected to the hoses and having sealing surfaces cooperating with the valve seats. The connection piece is rotatable together with the slide between a connected position in which the hoses are connected to their respective pipe lines, and a disconnected position in which these connections are shut off by the slide. The valve housing is preferably attached to one of the pipe lines and connected to the other one by means of a flexible hose.