| 摘要 |
PROBLEM TO BE SOLVED: To provide a backflow prevention basin provided in a drain passage in which drain water discharged from a septic tank flows and enabling ventilation between an upstream and a downstream in the drain passage.SOLUTION: In a backflow prevention device body 31, a handle part 33 constituted of a shell is formed, and one end of the handle part 33 communicates with a pipeline 14 on a drain passage downstream side, while the other end thereof communicates with a space Y which is in a basin body 2 and located higher than a pipe top of the pipeline 14 on a drain passage downstream side in a water outlet 4, and an internal space of the handle part 33 becomes a ventiduct 34. Moreover, a float valve 40 for preventing drain water in the pipeline 14 on a drain passage downstream side from flowing into the basin body 2 is provided in the ventiduct 34. |
