Backflow prevention valve and siphon drainage system

摘要

PROBLEM TO BE SOLVED: To provide a check valve capable of suppressing noise caused by passing air, and a siphon drainage system.SOLUTION: A check valve 38 includes a tubular part 44, a throttle part 48 extending from the tubular part 44, and an on-off valve 50 disposed at the tip of the throttle part 48, so as to make surface contact by an elastic force for closing a channel. The on-off valve 50 includes a cutout part 56A.SELECTED DRAWING: Figure 1