My apartment (top floor) has runs of 3/4" (-ish) pex-like tubing (photo attached, Switzerland if it's relevant) running from a central point. One such tube carries an existing coaxial cable (landlord provided, I do not want to detach) from a satellite splitter in my apartment to the roof, where, together with a large number of other such cables it emerges through a (non-removable) metal pipe about 4" in diameter with a 180 degree turn on.

My corona-virus challenge is:

  • to somehow thread a cat-6 cable up the same pex-like tubing so as to get internet access on my roof terrace (where the pipe is).
  • preferably to do the above with either no new tools or no tools I can't get by mail order.

EDIT: The pex-like tubing is not split (it's solid all the way around).

EDIT: I think I've now gained access to where the pex-like tubes end in the roof void. If I'm correct the cables emerge from many tubes, and are then cable-tied together to a cable frame in the open and go through what looks like some plastered gauze into a roof void, presumably into a pipe the opening of which must be about 15" above the gauze. So there are now two separate tasks: getting the cable up the pex tube (or down it having identified it), and getting it through the gauze and up the pipe (or the other way).

How would you approach the above?

enter image description here

  • 1
    Use a vacuum to suck a thread through may be one possibility. Then replace the thread with string then use the string to pull cable. But you will need luck... or use a cable puller...
    – Solar Mike
    Apr 9, 2020 at 10:45

4 Answers 4


I agree with Solar Mike that a vacuum may work to pull a string, If the smurf tube or flexible nonmetallic conduit is 1 piece. The nickname is from a kids carton where the characters are blue.

Having 9 or more flex lines going through a 4” makes me think this would not be 1 piece or the flex ends at the 4”, so you will need to try a fish tape.

A fish tape is a reel of steel or plastic that is used to push through a conduit, connect a wire and pull the wire back. The only problem(s) may be if the conduits stop prior to the 4” and the tape doesn’t go into the large pipe. The second possible problem is the 180 degree turn; depending on how tight this turn is, it may be tough getting a fish tape through depending on how far from the 4” pipe the flex conduits end.

If the smurf tube exits the 4” connect a vacuum and suck a string thru the tube a little plastic like a bit of bread wrapper on the end of the string helps the vacuum work. Fish tapes come in different lengths from 25’ to 250’, it will need to be as long as the length of the conduit.
Just finished and saw your edit I think a tape or combination of tape and string are the paths forward.

Good luck

  • Yup I think this is the way to go for the pex bit. From the gauze to the end of the pipe I suspect is a job for a bent coat hanger in the absence of anything more professional (I'd pop out to conrad.ch except for lockdown).
    – abligh
    Apr 9, 2020 at 12:02
  • Amazon has tapes with next day delivery.
    – Ed Beal
    Apr 9, 2020 at 12:04
  • And yes it seems "smurf tube" is the right term for it.
    – abligh
    Apr 9, 2020 at 12:04
  • in Switzerland? Just about everything errors out at checkout stage. [Found one that shipped, for $20 at an unknown date, so will try that]
    – abligh
    Apr 9, 2020 at 12:06

This is ENT (corrugated PVC), not anything like PEX

What you're looking at is most likely ENT (Electrical Nonmetallic Tubing, aka "smurf tube"), not any sort of tubing/pipe intended for plumbing work. Running a Cat6 cable through this should be not an issue at all, provided you stay within the fill limits of the ENT you are using. As Ed Beal mentions, you'll likely need to use a fish tape to pull either the cable itself, or a pulling string, through the conduit.


You will need to check carefully regarding the tubing. There is evidence that this tubing is the style that has a cut all along one side from end to end.

enter image description here

Tubing like this that has a split is designed to be used where the cable can be inserted into the tubing without having to thread it in all from one end. Such tubing is primarily used to protect the cable.

If the tubes are indeed the split type you are very likely going to have much difficulty trying to pull an additional cable through the tube without it spilling out of the slit as it goes around a corner.

  • Thanks. It's definitely not split and (per edit above) I think I've now found where these are likely to emerge in the roof space, which means I now have two smaller jobs.
    – abligh
    Apr 9, 2020 at 11:43
  • Michael I have never seen smurf tube split it’s entire length, I have seen automotive style protection but believe those splits may be from cutting to length.
    – Ed Beal
    Apr 9, 2020 at 12:03

I have and use rigid fibreglass poles- they can be threaded together and 'pushed up the stack. You'll need some sort of cone on the top to let it bounce out and around things, and if it bends tight it won't work at all.

Best way would be to disconnect the coax, time 3 strings and a new line to it, pull them all through, then pull the coax back in. Assuming it bends and turns a lot.

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