This article describes a new method of replacing gas or water mains without digging up the road over them. The rolldown technique, developed by the British 'no-dig' contractor subterra, passes polyethylene pipe through special rollers, to shrink it by rearranging its molecular structure. This narrower pipe is inserted into the pipe to be replaced; water is later passed through and 'pulsated' to restore the new pipe to its original size, so that it fits tightly inside the old pipe. Up to 14% more water or gas can be carried through the new pipe than through the old. Rolldown can now be used for pipes of diameter 3 to 12 inches (7.5 to 30 cm) but it is being tested on larger pipes which could include sewerage pipes. It operates at about the same speed as conventional alternative techniques, but with cost savings of order 20% to 55%, depending on the site, with largest savings for congested areas; it also significantly reduces disruption at the site and it is fairly easy to use. Rolldown has now proved to be an effective complement to other 'no-dig' techniques, and it could be suitable for as much as 30% of the annual replacement of gas, water and sewerage pipes in the UK.

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  • Corporate Authors:

    Reed Business Information, Limited

    Quadrant House, The Quadrant
    Brighton Road
    Sutton, Surrey  United Kingdom  SM2 5AS
  • Authors:
    • -
  • Publication Date: 1988-10


  • English

Media Info

  • Pagination: p. 16-7
  • Serial:
    • Volume: 170
    • Issue Number: 5015
    • Publisher: Hemming Group, Limited
    • ISSN: 0039-6303

Subject/Index Terms

Filing Info

  • Accession Number: 00487074
  • Record Type: Publication
  • Source Agency: Transport and Road Research Laboratory (TRRL)
  • Files: ITRD, TRIS
  • Created Date: Sep 30 1989 12:00AM