Most of the trenchless pipe repair methods used by DSD involve the insertion of a close-fit pipe liner into the pipeline to be repaired through a manhole. After insertion, the liner is expanded, cured, grouted or otherwise processed. Normally a lining operation can be completed in less than one day. The following are some common lining techniques :

Cured-in-place Liners

The liner is a soft continuous felt or glass-fibre tube. In a lining operation, a liner of the length of repair (the length of pipeline between manholes) is cut. It is impregnated with resin, pulled or pushed into the pipe through a manhole, and then expanded against the pipe wall by water or steam. The liner is then cured, usually by hot water or steam, for a few hours until it hardens.

Folded Liners

A folded liner is a circular PVC or polyethylene pipe folded into `U` or `C` shape (in the cross-section) in the factory to reduce the diameter so that it can be inserted into the pipeline to be repaired. After insertion, it will revert to circular shape by heating, applying water pressure, or release of physical constraint.

Machine Spirally Wound Liners

In this technique, a special winding machine is placed inside the manhole adjacent to the pipeline to be repaired. The machine helically winds a uPVC strip into a circular pipe, and launches it into the pipe to be repaired. After insertion, one type of liner is expanded to closely fit the pipeline to be repaired. For another type of liner, the annulus gap is grouted.