The film bag (1) has a predetermined breaking point (2) which is provided in a bag wall (7) to tear open under pressure without tearing any portion of film bag. The predetermined breaking point is located on an external wall side of the film bag. The breaking point is provided with a cover which is fixed by an adhesive. The cover is provided with a cover tongue to remove the cover manually or mechanically. The depth of the breaking point in the external wall of the film bag does not reach deeper than to barrier layer. Independent claims are included for the following: (1) a method of draining film bag; and (2) a device for draining film bag.
