Topic: electric cables, electrical equipment

Techniques for joining corrugated pipes

During the installation works of an electrical system, home automation or similar, it may happen that you are in the situation of having to join two corrugated pipes; in this case it is possible to operate in two ways: with special joints, or without joints.


Union of two corrugated pipes with joints: types of joints

The joints are found on the market in stores and warehouses of electrical materials, and allow very easily to join the corrugated pipes of the same section. Before going to insert the joint, the pipes must be trimmed in such a way as to eliminate burrs or imperfections, such as holes, etc. using a scissor that will bring the pipe back to a smooth profile. Once this operation is completed, the first tube is inserted inside the joint, in this case a compact cylinder made of a single piece, pushing slightly and rotating it for greater adhesion. When the tube has reached the middle of the joint it will stop because inside there is a sort of burr that prevents the tube from going further and there will be the necessary space on the other side to insert the other tube. Once both the corrugated parts are inserted in the joint, the entire part of the joint is covered with insulating tape. To be sure that the insulating tape does not come off, just pull it while applying it, so that it adheres as much as possible.

This is the simplest type of joint to use, but on the market there are different models of joints, fittings for corrugated steel, snap joints or reducers to join different diameter measurements.

There are also larger corrugated pipes pre-inserted under the floor of a building, rather than in plasterboard for example, or even under the road; in these cases more sophisticated joints exist, consisting of two shaped shell parts where the pipes are positioned, which are then tightened with bolts, also in stainless steel, and adjusted with a torque wrench, so as to guarantee water resistance and also resistance to external pressure and fraying.


Union of corrugated pipes without joint

It can happen to find yourself without joints, consequently you can opt to join the pipes in different ways depending on the cases:

  • two pipes of equal diameter: in this case one pipe of a larger size than the pipes to be joined must be used, for example to join two 20 mm pipes a 25 mm piece is needed, so that it can contain the two pipe units to be joined; with a scissors, a small cut is made along the two ends of the larger tube, so that the smaller corrugated can be easily inserted from each side. The result is a joint that does not prevent work with the wiring tool, the only final precaution is to tape all the part affected by the joint with insulating tape, paying particular attention to the parts that differ in size and slightly pulling the tape, to definitively join all the parts.
  • two pipes of different diameters: in this case, the smaller one can be inserted into the larger pipe, after making a small cut at the end of the larger pipe; the smaller one will then be inserted and the joint will always be closed with insulating tape, paying attention to make it adhere well and practicing several passes, to be sure not to run into detachments or slips.
    The alternative is that a piece of the larger tube is used to act as a joint, therefore as described above, this section will be cut in length and this will house both the larger and the smaller tube, then closing everything with insulating tape.
  • In extremis you can provide to join the two parts of the corrugated, previously trimmed as best as possible, feel to use any piece of pipe that acts as a "joint", but simply by joining them and sealing everything with the insulating tape, making more turns and pulling the tape, to avoid slipping; although this is not recommended.


Even these operations, which apparently seem trivial, are made with attention and care so that it does not happen that over time the joint is less and therefore creates problems for the system itself. Also in this case, it is advisable to have recourse to an expert professional, both to have a work done in a workmanlike manner and to remedy these problems.

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Posted by Redazione on May 13, 2020

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