# 2006 Washington DC
Polyethylene is a modern, environmentally compatible material that displays major potential for the substitution of conventional pipe materials. In the field of underground pipelines, polyethylene has unequivocally asserted itself as the material of choice for pressurised pipe systems. The polyethylene pipe in general is ideal for installation in the ground as it is particularly flexible, allows long sections on account of its drum delivery form, among other forms, can be longitudinally force-lock welded and is permanently leak-proof. A major advantage of the HD-PE pipe is its ability to resist static overloading or soil settlement better than rigid pipe materials. The lasting integrity of the connections, its high operational reliability, low pressure losses due to the smoothness of the pipe wall and the proven longterm behaviour underline the positive attributes of polyethylene pipes, with simultaneously high cost-effectiveness.
Since their introduction 50 years ago, compared with those of the first generation, the quality of polyethylene pipes has been consistently improved. The development of the materials in the past equally belongs to the success story of polyethylene pipes such as the improvement of the production procedures, which guarantee a permanent high level of quality.
For the currently available polyethylene materials, a product lifespan of 100 years is ensured on account of tests of the long-term creep under internal pressure pursuant to DIN EN ISO 12162, and the standard extrapolation method pursuant to ISO/TR 9080 (1, 2). Next to the enhancement of the long term stability up to 10 MPa the materials were optimized concerning crack-resistance and stabilisation (3). Thanks to the enhanced creep strength, higher operating pressures are now possible.
The majority of polyethylene pipes conform to the pertinent standards, such as DIN EN 12201 and DIN EN 1555-2. Installing techniques using a precisely defined pipeline zone and where the surrounding soil is prepared under appliance of the acknowledged rules of technology with a defined sandbed, the pipe is protected (acc. to DIN 4124, DVGW-W 400).
Moreover, various trends and applications exist and are evolving that ask for solutions that go beyond the regular standards system and further are able to cope with the future requirements.