Apparatus and method for maintenance of a device in a flow channel

The device has a flow channel (1), which consists of a wall section, in which a pH-measuring electrode (3), a drainage connector (11) and a supply connector (13) are arranged. A container is movably arranged relative to a wall section (5). The container is detachably arranged from the pH-measuring electrode, the drainage connector and the supply connector in a position, and forms a closed volume together with the wall section, where the volume is separated from the flow channel. A connector for a rinsing-and/or calibration medium inlet and outlet is arranged in the container. An independent claim is also included for a method for maintaining a pH-measuring electrode, drainage connector and supply connector that are arranged at a wall section of the flow channel.