A device for filling a flexible container and a method thereof are disclosed. The device may include a pressurizing chamber and an evacuation chamber. A first displacement piston is sealingly and slideably arranged within the pressurizing chamber to define an inner volume within the pressurizing chamber that is fluidly connected to a pressurizing conduit. A second displacement piston is sealingly and slideably arranged within the evacuation chamber to define an inner volume within the evacuation chamber that is fluidly connected to an evacuation conduit. A reservoir adapter is fluidly connected to the pressurizing conduit and connects to a liquid reservoir. A container adapter is fluidly connected to the evacuation conduit and connects with a flexible container. A transfer conduit is fluidly connected to the reservoir adapter and the container adapter. A valve fluidly connects the container adapter to the evacuation conduit or the transfer conduit.