An improved heat fused pipe assembly joint is provided using an internally positioned fitting having an annular insert portion substantially the same diameter as the internal diameter of the pipe section to be joined and a shoulder portion having a larger diameter. The pipe section is joined to the fitting by heating the pipe end sufficiently to soften it, heating the insert portion of the fitting so as to soften its exterior wall, inserting the fitting so that the end edge of the pipe section substantially abuts the shoulder portion of the fitting and crimping to cause fusion of the pipe to the fitting. For additional strength, the fused pipe joint assembly may be provided with an externally positioned sleeve.