The invention relates to a device for preparing a beverage, comprising:--a water reservoir (1);--a chamber (5) that is connected to said reservoir for delivering water;--means (17) for filling said chamber with water;--means (16) for emptying water from the chamber;--a compressed gas reservoir (2) with a three-way valve (4) for displacing said means so as to empty the chamber; and--a conduit (14) for conveying the water from the chamber to an extraction head.