performance and features: With three layer co-extrusion technology, advanced technique batch formula, co-extrusion ie having spiral channel and rotating core at a uniform motion,the line may be used to prouce core foamed pipe,pvc inner spiral core foam pipe and hollow wall inner spiral muffle draining pipe.this pipe has smallerspecific gravity,about 0.92~1.0g/cm3(for non foamed pvc pipe,it is 1.4g/cm3). Good sound insulation effect.as water dropping along the inner spiral of pipe will decrease noise 5~7 dbthan core foam pipe,ecrease noise 7~15db than soli wall pvc rigid pipe,and hollwe wall inner spiral muffleraining pipe decrease noise 20~30db solid wall pvc pipe.