In the construction market, the use PVC pipe has two kinds: One kind is a pressure pipe, other kind does not have the pressure tube. In the past the general use's cast iron pipe and the copper pipe took the pressure resistance building materials, not only corroded seriously, but also needed to maintain frequently and to replace, the cost was high. Presently,overseas constructs widespread use pressure resistance water pipe system, the hot water supply pipe mostly to use the PVC pipe. The small caliber PVC pipe (the UPVC tube, the CPVC tube) has the cost low, anti-corrosive, not to service and merits frequently and so on replacement. But the large diameter PVC pressure pipe (diameter in 100-900mm) substitutes the cast iron pipe, to strengthen the small putty pipe, the water supply system fluidity good, anti-corrosive, the weight is low. The electricity saving, the water quality quantity are good. But becomes spongy with the PVC sandwich layer without the pressure tube takes the indoor down-flow pipe and the rain water system tube, can very good solve the indoor down-flow pipe's noise problem. The public project pollution discharge tube uses not presses the PVC tube, has anti-corrosive, the hydrogen sulfide corrosion, the service life is not been long, the weight is light, the fabricating cost is low, easy to connect and to seal, is not easy to break. In addition, the structural purpose crossed wire tube and the buried cable protecting housing is also PVC tubing another market, at present domestic uses the variety is straight. expands the pipe, the double wall pipe and the single corrugated pipe