| 摘要 |
PURPOSE: A device for preventing back flow is provided to prevent a bad smell, sewage, and waste water from flowing backward. CONSTITUTION: In the case of a draining, a opening and closing valve of the device is lowered by the rising of a buoying material due to the flow-in of the sewage and a seal keeping part is opened by lowering of the opening and closing valve. The sewage is drained smoothly as a result. In the case of a drain failure, the opening and closing valve is lifted by the falling of a buoying material due to the self-weight and the seal keeping is closed by lifting of the opening and closing valve. As a result, a bad smell, sewage, and waste water are prevented from flowing backward.
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