The majority of FLOWTITE pipes are manufactured using the continuous advancing mandrel process, which represents the state of the art in GRP-pipe production. This process allows the use of continuous glass fiber reinforcements in the circumferential direction. For a pressure pipe or buried conduit the principle stress is in the circumferential direction, thus incorporating continuous reinforcements in this direction and not just chopped discontinuous roving such as in a centrifugal casting process, yields a higher performing product at lower cost. Using technology developed by material specialists, a very dense laminate is created that maximises the contribution from three basic raw materials. Both continuous glass fiber rovings and choppable roving are incorporated for high hoop strength and axial reinforcement. A sand fortifier is used to provide increased stiffness with placement near the neutral axis in the core. With the FLOWTITE dual resin delivery system, the equipment has the capability of applying a special inner resin liner for severe corrosive applications while utilising a less costly resin for the structural and outer portion of the laminate. (See section on Environments for special resin applications.)