Spiral Wound Pipe (SWP) is an in situ lining method which uses a specially designed winding machine placed at the bottom of an access chamber to helically wind a PVC profile strip to form a tube within the existing pipeline to produce a liner. SWP SL liners are structural liners with a design life of 50 years.

The major benefit of the SWP SL lining system is that sewer flows can usually be accommodated during installation, avoiding the need for by-pass pumping. The system maintains a hollow opening at all times along the length of the SWP during installation.


The specially designed winding machine is positioned at the base of the access chamber and the PVC profile strip is fed from above ground. Unlike the installation process for normal slip lining, it is pushed rather than pulled into the existing pipe. As the leading end of the tube exits the winding machine it rotates as it travels down the host pipe, forming a helix are added. As the SWP tube which is formed is of a smaller diameter than the host pipe, the rotating tube “rides over” pipe defects, such as displaced joints and fractures.

Once the smaller diameter tube has reached the target access chamber, it is braced and locked into position. The annulus between the new spiral wound pipe and the host pipe is then filled with a cementitious grout.

Sizes and Materials

The SWP SL method is available for larger pipe from 750mm to 2,500mm in diameter. The profiles used in SWP SL linings are manufactured in quality-controlled factory conditions, using PVC which has a proven record for sewer applications worldwide.