Polyvinyl Duct (PVS)
Sheet Metal Connectors, Inc. PVS spiral pipe is formed from a coil of metal into a rigid PVC tube with a 4-ply spiral lockseam. It has smooth interior for low friction loss with the grooved seam entirely on the outside. This pipe has a resistance to crushing approximately 2 1/2 times that of longitudinal lockseam. Optional corrugations are available which increase the rigidity of the pipe by approximately 300%. Pipe sections can be joined together by an E-Z Flange with Barrel Clamp, E-Z Flange Jr. with Barrel Clamp, or Standard Spiral Pipe Connector.
http://www.smcduct.com/polyvinyl-coated-underground-duct-systems-and-fume-exhaust-systems-catalog/Polyvinyl Duct (PVS) Catalog & Specs