Product Description:

Spiral Wound Pipe (SWP) DiaFit is an in situ lining method. A specially-designed winding machine is placed at the bottom of an access chamber to helically wind a PVC profile strip and convert it to a tube that conforms to the existing pipeline to produce a structural liner with a design life of 50 years.

The major benefit of the SWP DiaFit 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 winding machine is placed at the bottom of the access chamber. A manufactured PVC profile strip is then fed into the machine from above ground. The winding machine pushes the profile stripe down the pipeline as a continuous helix. Unlike installation methods for slip lining, the new lining strip is pushed, rather than pulled, into position.

As the SWP helix strip forms a lining smaller in diameter than the host pipe, the rotating tube ‘rides over’ displaced joints and surface irregularities as it moves along the host pipe.

When the PVC tube reaches the target access chamber, it is locked into position into prevent it from turning. The winding machine then continues to turn the newly wound pipe, which progressively expands the tube until the entire length forms a tight fit (DiaFit) against the inner surface of the host pipe.

Sizes and Materials

Suitable for circular non-pressure pipes ranging from 225mm to 600mm. The profiles used in SWP DiaFit linings are manufactured under quality-controlled factory conditions, using PVC which has a proven record for sewer applications worldwide.