| 摘要 |
The invention relates to a filter (1) which has a backwashing system (2) comprising a plurality of members in the form of slotted stainless steel pipes or tubes, or "laterals", (3) extending laterally of the filter below the filter medium, sand in the embodiment, each tube being substantially parallel and each being connected in the embodiment to a manifold or air supply pipe (5) by a respective supply means or downpipe (6). Each tube (3) has a plurality of longitudinally extending slots (7), through the circumference of the tubes, the slots being in the embodiment 0.25 mm in width and being arranged in groups of three at different "levels", the two "upper" (7', 7'') ones as viewed and as in use being angularly spaced by 120 DEG , and the lower one (7''') being in use on the floor of the filter. The slots are preferably formed by a laser cutting device to provide uniformity of width and length, and with little or no swarf.
|
