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).
