The invention relates to a connecting device for connecting a first reservoir to a second reservoir, with a first section (11) for placement of the first reservoir (5), closed by a closure piece (51)； a second section (12) for placement of the second reservoir； and a piercing element (2) which, when the first reservoir (5) is placed on the first section (11), punctures the closure piece (51) of the first reservoir (5) with a piercing end (21). According to the invention, the piercing element (2) can be moved from a first position to a second position, such that, in the first position, it blocks a flow connection between the first and second sections (11, 12) and, in the second position, permits a flow connection between the first and second sections (11, 12).
