Abstract: A double containment pipe fitting (10) has inner and outer pipes (12, 14). The inner pipe has a polygonal cross section to present a number of edges (12j) which extend parallel with the longitudinal axis (15) of the pipe and engage the inner surface (14c) of the outer pipe to present the double containment feature, namely the central portion of the inner pipe being one fluid flow path and the spaces (18) between the flat outer sides (12c) of the inner pipe and inner surface of the outer pipe forming the second fluid flow path. The outer surface of the inner pipe can be triangular, square, rectangular or otherwise polygonal.