| 摘要 |
Outlet valve (2), for water which has flushed-clean filter materials (4, 5) of differing densities in a water purification basin (1), comprising a fixed lower tube (11) with an upper tube (10) inside it which acts as a weir, has the upper tube (10) movable in accordance with the sedimentation of the filter materials (4, 5). The upper tube is steered along guides inside the tubes. A guard fitted in the upper part of the movable tube prevents filter material reaching the outlet (33). A scraper attached to the lower tube prevents dirt coming between the movable and fixed tubes. The scraper is of preformed polyethylene.
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