A pressure control system provided for maintaining a constant predetermined excess pressure in a fluid dispensing container comprises a high-pressure plastic vessel having an inner chamber, and a pressure control device having a valve and mounted on the open end of the high-pressure vessel, whereas a passageway is provided from the inner chamber to the outside, which is controlled by the valve. A piston with a protruding stem is provided in a guide member, whereas between the guide member and the piston a chamber with a gas with a reference pressure smaller than the high pressure is enclosed, and the high pressure vessel is closed by a closure with a central bore of smaller diameter than the diameter of the stem, and the piston end remote from the protruding stem is pressurized by the fluid in the fluid dispensing container.