Flow-control system includes a fluid reservoir configured to store a fluid, a pressure accumulator in flow communication with and positioned downstream from the fluid reservoir, and a loading zone that is configured to receive and fluidly couple to a flow cell having a biological or chemical sample. The loading zone is in flow communication with and positioned downstream from the pressure accumulator. The flow-control system also includes a system pump in flow communication with and positioned downstream from the loading zone. The system pump is configured to induce a flow of the fluid from the fluid reservoir and through the pressure accumulator and the loading zone. The pressure accumulator is configured to receive fluid from the fluid reservoir during a filling operation. The pressure accumulator is configured to impart pressure on the fluid and drive the fluid toward the loading zone during a pressure-assist operation.