| 摘要 |
A back-water trap unit comprises a housing having an outer perimetric wall sealed to a base to define an enclosure, and a removable housing cover comprising inlet apertures. An interior wall, shorter than the housing wall, is sealed to the base to define an inner compartment and an outer compartment within the enclosure, the inner compartment being sealed by a cover secured to the upper interior wall edge and the inside of the housing wall. A flapper valve secured to the interior wall within the inner compartment is rotatable in response to liquid pressure to open or close an inlet aperture proximate the lower interior wall edge. An outlet through the housing wall as high as or above the upper edge of the inlet aperture allows discharge of fluid from the inner compartment, while the flapper valve prevents unwanted back-flow from the inner compartment to the outer compartment.
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