A thin ribbon (5) spirally wound polymer conduit (37) and method of forming, wherein a helical reinforcing bead (8) is interposed adjacent overlapping layers of ribbon (5). Further, a method of continuously forming spirally wound conduit (37) wherein a sacrificial layer (17), preferably having a different base polymer to that of the conduit (37), is first applied to the former (1) before the conduit (37) is formed overtop.