Sampo Industrial manufactures a range of seamless copper tubes supplied for use in sanitary drainage, waste, vent piping, soil and other non-pressure uses. Standard Diemntions, Weights, Tolerances in Diameter and Wall Thickness. The standard drainage grade copper tube is identified with continuously ink-marking along its lengths indicating "DWV", manufacturer's name, country of origin, conforming = minimum wall thickness of tube (mm) back to the origin of manufacture. END-CAP : NO END-CAP INK MARKING : YELLOW INCISION : TRADEMARK OF THE MANUFACTURER + DWV