A method and assembly for sealing an opening in a pipe wherein the opening is a damaged/cracked section in a length of pipe or the junction between a main pipe and a lateral pipe. The assembly includes a sealing member attached to a positioning tube such as preliner. The sealing member is combined with the preliner so that when the assembly is positioned in the main pipe, the sealing member corresponds with the opening. The sealing member is sized such that it extends along the main pipe on opposite sides of the opening. A mainline liner is installed within the preliner. In some embodiments, after the mainline liner cures and hardens, a cutter is used to cut an opening in the mainline liner, preliner, and sealing member to reinstate service to the lateral pipe. The sealing member remains in place around the periphery of the lateral pipe junction to act as a water stop at the opening.