Caisson secondary water discharging system with air returning pipeline

The utility model discloses a caisson secondary water discharging system with an air returning pipeline. The caisson secondary water discharging system comprises an upper stand pipe, a conduction piece and a lower stand pipe which are sequentially connected from top to bottom, and further comprises a horizontal water discharging pipeline which is connected and communicated with the conduction piece, and a closestool connection pipe and a floor drain connection pipe which are connected and communicated with the horizontal water discharging pipeline, wherein an air returning pipe for communicating the conduction piece with the floor drain is arranged between the conduction piece and the floor drain. According to the caisson secondary water discharging system, the stench returning problem can be completely solved; particularly, in a washing process, air passes through the air returning pipeline to return back to the floor grain so that vacuum is not formed in the pipeline and the resistance is reduced; the conta