Abstract: This method for the trenchless, in situ repair of underground pipe includes the steps of isolating a section of pipe to be repaired, heating a sealing material (having predetermined physical and chemical properties) to a liquid state, pumping the liquid material, under pressure as required, into the isolated section of pipe; circulating the liquid through the isolated section of pipe; and forcing the liquid into and through cracks in the pipe and into the soil surrounding the pipe. This is a thermal process wherein the molten material which is forced into the cracks and soil, cools and solidifies. The remaining liquid circulates through the isolated section of pipe and stays in a liquid state, because of retained internal heat, until it is removed from the pipe for storage and reuse. With this process, a novel bottom plug is used which allows the sealant to be applied to all cracks, crevices and even openings found where the smaller pipe connects to the larger pipe.