A collecting tank for a heat exchanger pertaining to a motor vehicle cooling installation includes a tank element. The tank element includes at least two collecting regions for receiving fluid, the receiving regions being embodied together as a single component and being outwardly sealed by a sealing element, and a bottom for closing the collecting regions. A sealing arrangement is provided between the tank element and the bottom, between two adjacent collecting regions. The sealing arrangement includes exactly one sealing element which, in addition to sealing between the two collecting regions, is used to seal the arrangement towards the outside. The sealing element is preferably arranged in a plane in the collecting tank, especially in a continuous channel.