The MWSL is initially wound at a fixed diameter smaller than the host pipe. This is done so the liner can negotiate offsets and other host pipe defects without restriction. SPR™EX liners are typically installed from the downstream to the upstream manhole however reverse set-ups are possible.

Once the SPR™EX liner reaches the upstream manhole, the liner is torsionally restrained. The expansion process begins when the wire positioned between the primary and secondary (or sacrificial lock) is retracted, severing the secondary lock. This allows for successive wraps of PVC profile to expand, creating a customized tight fit liner against the inside of the host pipe. As the wire is pulled, the liner continues to expand. The operator will  feed additional profile into the host pipe until the entire pipe segment is a close-fit.