Gas/liquid separating devices include a separator (1) for separating a mixed gas/liquid flow (M). A liquid drain (2) communicates with the separator and defines a liquid storage chamber (30). The liquid drain serves to temporarily store a liquid separated from the mixed flow within the liquid storage chamber, so that a space that is not occupied by the liquid is ensured within the liquid storage chamber. An adjusting mechanism (52, 152) may serve to adjust the pressure within the space of the liquid storage chamber.