A pressure regulating system (1, 16, 19) for discharging a liquid with a predetermined liquid pressure from a liquid opening (10), comprising an elastic bag (3) with a liquid phase (9) and a gas phase (8), the liquid opening being formed in the lower region of the elastic bag (3) when the elastic bag (3) is in the operating position, at least two push elements, at least one drive unit (4) and a control unit (5). The elastic bag (3) has a gas opening that extends into the gas phase (9). The pressure regulating system (1, 16, 19) has a ventilation unit (6) which is connected to the control unit (5) for communication and which connects to the gas opening of the elastic bag (3). By introducing and/or removing gas into/out of the elastic bag (3), the ventilation unit (6) regulates a liquid pressure of the liquid discharged through the liquid opening (10).
