Drainage Element and apparatus and method for making same

摘要

A preassembled drainage line element is fabricated with one or more flaps. In one embodiment, the drainage line unit is made from a webs of net material and a web of water permeable material and has two flaps at diametric points. The webs are formed about a barrel and the longitudinal edges are secured together, as by sewing a seam, to form a flap. The seam can be sewn at one of a plurality of spacings from the barrel to form a drainage line element of a different diameter from a standard diameter without need to adjust or replace other components of the fabricating machine.