From April 19 to 22, 2004, the Plastics Pipes XII Conference took place in Milan, Italy. During this conference, Dr. J. Hessel (together with co-authors A. Lueghamer and M. Tsunaga) presented a lecture titled "Abstract welding of large diameter heavy wall polyolefine pipes and long term performance". This lecture compared various welding techniques, standards, and guidelines for butt welding of HDPE and PP pipes. Test studies on weld quality (long-term and short-term tests) were conducted on large, thick-walled polyethylene pipes, considering the influence of raw material quality and wall thickness. Practical experience with the installation of thick-walled large pipes and the method for determining the expected service life of the pipeline demonstrate the superiority of polyolefin pipes over other pipe materials. An example is a butt-welded HDPE pipe (outer diameter 710 mm; SDR 13.6; PE 100) in the city of Misato, Saitama Prefecture, Japan, in a water distribution system with land realignment.