Method of forming a conduit

A method of continuously forming conduit comprising:

• providing a thin polymer ribbon,
• heating said ribbon to soften said ribbon, and forming a crease approximately midway across said ribbon, said crease being substantially parallel with said ribbon,
• supplying said creased ribbon having “leading” and trailing” lateral edges, spirally around a former with the leading edge of each turn of ribbon overlapping the trailing edge of a previous turn of ribbon on the former and the trailing edge of each turn underlapping the leading edge of a succeeding turn,
• said former and rotating and advancing said conduit, and
• applying a bead of molten plastic material to said lapping edges of adjacent turns of ribbon, such that said bead welds said adjacent edges of said ribbon and forms a helical reinforcement to said conduit when cooled.