We are moving to a new flat. This flat has many empty sockets in the walls. These sockets are connected using empty corrugated pipes, so one can put additional cables through them.

I want to use these empty sockets/pipes to put CAT 7a cables into the wall, with CAT 6a outlets in every room.

My question is: How do I find out from where to where those empty pipes go?

I already tried two things:

  1. I tried to push a cable through them, and check where it comes out of the wall. This worked for some connections, but for many the cable gets stuck and I cannot find the other end of the pipe.
  2. I also tried to put a thread with a bit of paper on it into the pipes, and suck them out somewhere else with a vacuum cleaner. This also worked for some connections, but I need to check every other pipe end in the flat to find the correct one. And it makes a lot of noise (the pipes resonate).

I thought of pumping some sort of smoke into a pipe using a compressor, and look where it comes out, but I have neither a compressor nor means to produce smoke in a safe way.

Any other ideas?

Edit: Here is a picture of one of the sockets, with the CAT 7a cables already put through them:

enter image description here

  • 2
    Hello, and welcome to Home Improvement. A picture of one of these "sockets" would be very helpful. Commented Dec 26, 2018 at 10:37
  • 1
    I assume that by corrugated pipes you mean flexible steel electrical conduit? Commented Dec 26, 2018 at 19:41
  • 1
    @MikeWaters: With corrugated pipes, I mean this
    – Jost
    Commented Dec 27, 2018 at 10:44
  • @DanielGriscom: Thanks :-) I will upload a picture as soon as I was able to make one - much to do currently with the moving.
    – Jost
    Commented Dec 27, 2018 at 10:44

1 Answer 1


The basic tool for installing wiring in conduit is a fish tape

Ideal brand fish tape

It's nothing more than a stiff strand of steel, plastic, or fiberglass made to push into conduits. You push it through the conduit, tie your wires to the end of it, and pull it back through.

When you're not sure where the conduit goes, you will want a non-conductive fish tape - you don't know if it might come in contact with live wire, in an electrical panel, etc.

  • 1
    Thanks, that was the solution. The thickness of CAT 7a cables makes it hard to just tie the cable to the fish tape and pull it through, so I used tape to glue cable and fish tape together at a length of 30-40 cm. That did the trick, though I needed to push the cable from one end and pull the fish tape simultaneously from the other end.
    – Jost
    Commented Jan 14, 2019 at 8:21

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