The present invention relates to a degassing system (1, 23) with a control device (17, 36), a degassing tank (2, 24) with a first space area (3, 25) configured for having liquid introduced therein and a second space area (4, 26) configured for having the liquid from the first space area (3, 25) introduced therein. The first and the second space area are partially separated from one another by a separation element (5, 27). A controllable pump (15, 34) is provided, which pumps liquid from the first space area to the second space area for a two-stage vacuum degassing process, when the pump is operated. The control device controls the pump such that the pump will not be operated for a single-stage vacuum degassing process and will be operated for a two-stage vacuum degassing process. Furthermore, the present invention relates to a method of executing a degassing process of a liquid making use of a degassing system according to the present invention. In addition, the present invention relates to a beverage treatment machine comprising the degassing system and a filling plant arranged downstream of the degassing system.
