A modular beverage dispensing assembly (1) having a number of beverage storage units (2), each for supplying a pressurized beverage and in turn having an airtight pressure container (3) housing a collapsible removable cartridge (4) containing the beverage; and an electric compressor (5) for feeding pressurized gas into the pressure container (3) of each beverage storage unit (2), to crush the removable cartridge (4) inside the pressure container; each beverage storage unit (2) also having a valve assembly (12) for regulating pressurized-gas flow from the pressurized-gas source (5) into the airtight pressure container (3), and which has a non-return valve (25) and a three-way valve (26) arranged in cascade formation one after the other; the non-return valve (25) being interposed between the inside of the pressure container (3) and the three-way valve (26), and being so oriented as to allow pressurized-gas flow from the pressure container (3) to the three-way valve (26), and to normally prevent pressurized-gas flow into the pressure container (3); the three-way valve (26), on the other hand, being designed to connect the non-return valve (25) directly to the pressurized-gas source (5) when the pressure container (3) is in a predetermined work position, and to connect the non-return valve (25) directly to the outside when the pressure container (3) is not in the work position; the valve assembly (12) also having valve-locking means (28) for keeping the non-return valve (25) open when the collapsible removable cartridge (4) is inserted properly inside the pressure container (3).