Abstract: A substantially cylindrical drainage unit for use when buried in soil as part of a wastewater leach field comprises a first plastic bead aggregate mass, optionally with a central perforated pipe, surrounded by a segmented-quilt exterior surface. Quilts are held in place around part or all of a drainage unit by straps, a circumscribing netting sleeve, or by being themselves in the form of tubular sleeves. Preferred rectangular quilt segments contain a second pebble aggregate that is smaller than the first aggregate. Quilts are fabricated by mating two horizontally-moving layers of geotextile and disposing the second aggregate into channels or cavities that are defined by seams that join the layers to each other.

Abstract: A plastic leaching unit for receiving water when buried in trenches in soil comprises a plurality of pillars interconnected by struts. A canopy made of sheet material is attached to the tops of the pillars. Preferably, the canopy is perforated and is overlaid with geotextile. The pillars are arranged as spaced apart integral assemblies to enable lateral and vertical bending of the leaching unit, for conforming to a not-straight trench. Leaching units may be stacked one upon the other within a trench.

Abstract: A substantially cylindrical drainage unit for use when buried in soil as part of a wastewater leach field comprises a first plastic aggregate mass that is contained within netting, with an optional central perforated pipe. A segmented quilt comprises the exterior surface of the drainage unit which is in contact with soil. Pebble aggregate that is smaller in particle size than the first aggregate is contained with the cavities of the quilt segments. Quilts having different segment shapes and sizes are manufactured by specialized apparatus which creates rectilinear or serpentine seams.