In general, pipes with wavy outer layer which have alternating ridges and troughs is named corrugated pipes. The pipes can be produced by plastic (such as Polyethylene and PVC) or metal. The shape of outside layer makes the pipe more flexible in length. Low price which is result of using less raw material is one of the main characteristics of these pipes.
©Normal corrugated pipes contain two layers in which the outside layer with the wavy shape is named profile of the pipe. In contrast, the inside layer is smooth which makes the fluid to transported faster inside the pipe.
With the changing in height, shape and thickness, or distance of the Profile of the pipe it’s possible to change the resistance of the pipe against outside pressure. The inside layer do not have such an effect on stiffness of the pipes and as it mentioned it just makes the fluid transported with higher speed and flow.
It’s possible to produce corrugated pipes with different color in outside and inside layers. These colors can be changed by the color of the masterbatch is added to the raw material of PE by the percent of 3 in the process of production. Usually, the color of outside layer is Black which has more sustainability against UV ray in the sunlight. In this case, there is no need to add Anti-UV to the raw material. In comparison, in the small diameter of pipes, the inside layer has a light color so if there is a hole or any crack it can easily observed. In Iran, normally, the inside layer of corrugated pipe is yellow.
As it mentioned in above, one of the physical advantage of these pipes is flexibility which is resulting to more durability against outside pressures. If the percent of compaction around the pipe after the installation process is suitable, most of the external loads transported to the surrounded soil and the pipe itself will tolerate less load. However, in concrete pipes, all the external load should be tolerated just by pipe and the surrounding soil do not have any effect in it. So, in the same condition PE pipes are produced with less stiffness than concrete pipes.

Connection of two corrugated pipes
Coupler and ring
In this kind of connection, the ring should be placed in the last trough of two pipes and insert that end parts to the coupler. There is a possibility of changing in the length of both of the pipes in this kind of connection.

Socket and ring
In this kind of connection, there should be a socket at the each end of the pipe which is provided in the process of production. After placement of ring in the last trough of each pipe, there is a need to insert that end to the socket part of the other pipe. This installation is easier and faster in comparison with previous type.