Do You Really Understand How a Refrigeration Check Valve Works? A check valve plays a critical role in keeping your refrigeration system efficient and your compressor protected. It allows refrigerant to flow in only one direction — preventing backflow that can cause compressor damage or system inefficiency. You’ll often find them on liquid lines, discharge lines, or parallel compressor systems to stop reverse flow during shutdown or defrost. A stuck or leaking check valve can lead to issues like