Abstract: A method of joining a first pipe having an outer surface and an annular end face and a fitting having an end face surrounding a shoulder recessed therein which includes inserting a spacer having a predetermined thickness and formed of a synthetic resin into the recess in abutment with the annular shoulder followed by inserting the annular end face of the pipe into the recess until the annular end face, the spacer and the annular shoulder are in mutual contact, temporarily tack welding the pipe to the fitting to establish spacing between the annular end face of the pipe and the annular shoulder of the fitting, and permanently welding the pipe to the fitting. In one embodiment, the heat from the permanent welding step vaporizes the spacer leaving a gap of predetermined size between the confronting annular end face of the pipe and the annular shoulder of the fitting.