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In my newly-built house, an empty conduit was added into the foundation so that an antenna cable could later be pulled through. The conduit is around 9 meters long and has three 90-degree bends with a radius of around 30cm. The conduit is a corrugated PVC pipe similar to this image with 25mm diameter.

Today, an attempt was made to pull a coax cable. I first pushed a nylon puller through (perhaps the wrong term, but it looks like this) from inside the house to outside (into the garage). That was a little difficult but I got it through. I then attached the coax on the puller; I used a wire to tie them together (I now know that I should have used tape).

Then I pulled it back inside again, but after some meters it came undone, so the puller was completely removed from the conduit while the coax was only about halfway through. I was able to pull the coax some way back out again, but now it's stuck about 3 meters inside the conduit. I measured this by feeding the puller into the conduit alongside the stuck coax until it wouldn't go further. I removed the puller again.

The coax seems to be stuck. I can't push it in and I can't pull it out. I don't dare pull at it too hard because I know that the coax isn't very strong and if it snaps off inside then I have no way to get to it.

The conduit runs underneath the house, it lies in concrete under the flooring, so I can't get to it without tearing half the kitchen apart, tearing up the parquet flooring, tearing up the underfloor heating, and so on. Absolutely not an option. There's no spare conduit either; this is the only one and if I can't use that then I have no idea how to get an antenna signal or sat cable into the house. That would be ... very bad.

Okay -- I've just learned how not to pull coax. Can you now teach me how to get it unstuck?

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How tight are the 90 degree turns? Some gauges of Coax aren't designed for super sharp bends. At this point, I'm not sure what advice to give you. I imagine pulling as hard as you can is likely the only option. –  DA01 Aug 30 '13 at 22:27
    
The radius of the turns is around 30cm. –  Torben Gundtofte-Bruun Aug 31 '13 at 5:54
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1 Answer

Unless it is extremely thick co-ax, like RG-35, there should be plenty of room to slide the nylon fish tape from outside along the stuck co-ax. Probably the wire you wrapped around it for attaching to the fish has formed a barb—how apropos for a fish! :-)

Push the fish past the end of the co-ax a little bit (or as far in as it will go), and then alternately pull the fish back and then jab it forward in a series of vigorous thrusts intended to make it slide past the end in a random new location each thrust and, if it hits the target, bend the barb out of the way.

If that doesn't do it, get some silicone lubricant or any other non-drying lubricant, blob it liberally on the end of the fish and push it in to the end of the co-ax in an effort to lubricate the area, twist it around a bit, and then withdraw the fish and repeat 6+ times to be sure there is lots of lube in the conduit. Remove the fish when done.

If the conduit where the obstruction exists is surrounded by concrete, I would try giving the co-ax a sharp, swift, hard pull to see if it can be budged into the lube. If it is not so well supported, then pull gently at first and gradually build up force allowing the co-ax to stretch: if it can be made a little thinner, it might let go.

Give that a go. I have some more half-baked ideas if that doesn't work.

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The cable pulling lubricant and spinning/twisting the cable are probably the two best ideas. With any luck, one or both of those should work the line free. –  BMitch Aug 30 '13 at 23:12
    
Thank you - I tried this without luck. The coax is so far in there that I can't really get any lube to the relevant spot, and the fish won't really get there, it's difficult. The barb theory sounds right, but twisting the coax also didn't help; I guess I can't twist it enough in the open end to effect any movement at the stuck end. I'm worried that it's thoroughly stuck! I welcome your half-baked ideas...! –  Torben Gundtofte-Bruun Sep 12 '13 at 18:11
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