Abstract: A filter is provided with a number of elongated filter elements disposed in a pressure vessel. Each element has a filter web extending about the length of the element and fastened at the top and the bottom. Rigid support means are provided inside the filter element in order to support the web. They extend about the length of the element and preferably extend over a part only of the circumference of the element so as to permit the web to perform a limited movement outwards and inwards in radial direction. During the operation the web is pressed against the support means by the inflowing liquid permitting a filter cake to build up at its outside while upon a backwash operation the web moves outwardly away from said support means thus loosening the filter cake. Inlet and outlet means are provided on the pressure vessel. This permits a build-up and easy removal of the filter cake without the use of a bellows type filter web.

Abstract: Filter element for a pressure filter container, composed of a central tube surrounded by a plurality of support tubes for supporting a filter web. The support tubes can be closed or perforated. The space between the central tube and support tubes, as well as the interior in the case of perforated support tubes, serve as flow canal for the filtrate. The use of plastic tubing provides a simple and cost-favorable filter element.

Abstract: A backwashing alluvial filter has a vertical filter container, a plurality of collecting pipes removably mounted in the container, a plurality of filter elements suspended on the collecting pipes, separating walls subdividing the interior of the filter container into at least two chambers, and communicating with one another via vertical overflow shafts. Washing off of solid matter is performed by supplying a washing liquid via pipes directly under the overflow shafts.