I have an existing exterior conduit entering my house, carrying low voltage (CAT6, Coax) wires from our detached garage to my inside equipment room. I need to bring a new fiber-optic cable (for fiber internet) into the same equipment room in the same location where this conduit terminates. My goal here is to avoid having to drill additional holes in the side of the house to bring the cable inside, and see if I can somehow tap into the existing conduit body on the exterior.

Since the conduit contains existing wires, I can't just replace the conduit body with one that has an extra connector. Is there some type of conduit body extension that would bolt in between the existing body and the lid and provide for another ingress point into the conduit? If so, what is it called?

Inside the house, the conduit goes into a junction box, before continuing through flexible interior conduit to the final destination. Worse case, I could drill the wire through next to the conduit body and I still should be able to get it into the junction box to get into the interior conduit for the final segment.

exterior conduit bodyexterior conduit body

  • 1
    How are you getting the fiber-optic to this location,? What's preventing you from using the exist box? May 30, 2020 at 22:41
  • Is this new fiber coming in from an overhead drop? Does the existing conduit terminate in an enclosure (box, cabinet) within the equipment room, or does it just discharge into the wall cavity or into the room itself using a belled end? May 30, 2020 at 22:53
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    econline.com/doc/conduit-body-junction-box-0001 or perhaps you can use a cover plate with conduit port from one of the "universal" conduit bodies: rexelusa.com/usr/Root-Category/Fittings/Conduit-Bodies/…
    – Ecnerwal
    May 31, 2020 at 14:17
  • 2
    Ecnerwal has provided the ans to your question- Use the expansion or addition port cover in lieu of the original cover. Add a bottom loop to the cable before going into the box shown. The real issue you face is that the fibre cable has specific bend radius so you have to make sure is not exceeded in the entry to the house, and in the jb on the other side. On the other side (interior), the fibre could just be run on the surface to your rack and NOT run through the EMT conduit with the other com cables. Jun 1, 2020 at 0:41
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    Most modern drop cable uses Reduced Bend Radius fiber (which is a remarkably small upcharge when buying the cable) to make installing it into houses practical. Do, of course, check what the minimum bend radius is (ask the provider.)
    – Ecnerwal
    Jun 1, 2020 at 2:52

1 Answer 1


tl;dr I wasn't able to achieve the install without another hole, but it all worked out cleanly in the end.

Thanks to all who commented on this, your insight was helpful as I thought through how to do this. Ultimately, I wasn't able to find an actual port cover or extension ring anywhere -- seems like a potential business opportunity, but maybe this is a rare scenario :)

Today was install day, and ultimately it was quite successful. Since a slackbox was required to hold the excess fiber, and combine the outdoor and indoor cables, the tech drilled a 1/4" hole through the back of the interior junction box to exit the house to the right of the conduit body. The fiber enters the back of the slackbox and it's a nice clean look. It's sealed up with silicone, and just needs a coat of paint to make it blend in to the house. The aerial fiber comes from the pole and down behind the downspout.

exterior fiber slackbox

On the inside, we attached pull string to one coax line in the wiring cabinet and pulled it into the junction box. Then, we attached the fiber to the coax (along with another pull string for the future), and re-pulled it back to the destination. It's basically a straight run along an interior wall, and worked out great. The ENT is 1.5" diameter, I believe, to answer a prior comment. It's got a bunch of wires in there, but there was plenty of room for the fiber. And yes, the interior cable they used is pretty bendable, so had no issues in that regard.

interior junction box

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    Thanks for coming back to answer your own question! Please be sure to select it as the "correct" answer, too. That looks like a very nice, neat, tidy installation both inside and outside.
    – FreeMan
    Jun 4, 2020 at 13:00

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