HDPE lining offers the sewer structure several additional advantages that are not always appreciated. Its surface is smoother than concrete, and thus a pipe with a smaller internal diameter can be used. Alternatively, the same diameter can be used at a flatter gradient. The long-term pullout strength of the lining anchors is able to cope with a ground water pressure in excess of 10m. If necessary the HDPE lining can be welded together at the joints by applying a bead of HDPE to make the lining continuous and create a water- and gas-tight joint. The abrasion resistance of the HDPE is actually greater than that of concrete.
Concrete pipe with a cast in HDPE lining has all the advantages of a strong rigid pipe that keeps its shape as well as those of a plastic pipe that is inert to acid attack. It is the best pipe for large diameter gravity pipelines in almost any condition.