Abstract: A double-containment thermoplastic pipe assembly provides for transfer of differential thermal expansion forces to rigid external supports. The assembly includes a flanged restraint coupling having an inner carrier pipe portion, an outer containment pipe portion, a wall connecting the inner and outer pipe portions, and a radially extending flange around the outside of the containment pipe portion. The flange is secured to an external support such as a manhole for underground system by being cast into the wall of a cast-in-place manhole or by being engaged by rings on each side of the flange for precast manhole systems. The outer pipe terminates at the manhole wall so that the containment function within the manhole is performed by the manhole inself. For above-ground applications, the coupling is secured by engagement of the flange with a cast concrete wall or metal saddle connected to an underground footing.