| 摘要 |
In a drainage clean-out pipe 1 comprising a pipe section 2 having an upstanding shaft 3 closed by a cover 7, the cover carries at least one depending plate 10 whose periphery engages sealingly (as at 120 within the pipe 1, the plate 10 having a drainage passage providing a seat 14 for a valve 19 preventing back flow. As shown the cover 7 carries two depending plates 10 each of which carries a flap valve 19 so that removal of the cover also removes both back flow valves 19. In a modification, each flap valve is replaced by a freely-moving ball float valve (one shown at 19a) rolling on an inclined guide 21. <IMAGE> |
