The structure of lift check valve is similar to that of stop valve, only lacking the stem to drive the valve disc. The medium flows in from the inlet end (lower side) and out from the outlet end (upper side). When the inlet pressure is greater than the sum of the disc weight and its flow resistance, the valve is opened. On the contrary, when the medium flows back, the valve is closed. Swing check valve has an inclined disc that can rotate around the shaft. Its working principle is similar to that of lift check valve.