Multi-layer tube and process of making the same

A method of producing a multi-layer tube, the method comprising

• extruding an inner-layer formulation to form an inner parison,
• extruding a core-layer formulation comprising an HDPE resin to form a core parison,
• extruding an outer-layer formulation to form an outer parison,
• aligning the inner parison, the core parison, and the outer parison to cause the core parison to be located between the inner parison and the outer parison to cause the core parison to surround the inner parison and to be surrounded by the outer parison to form an extruded multi-layer tube,
• wherein the core parison has a density that is less than a density of each of the inner parison and the outer parison.