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I have a PoE camera and the wiring is about 3 feet too short. The Ethernet that was pre-wired is about 100 feet and it isn't practical to redo the wiring.

How should I extend the cable? The connection may be exposed to a little rainfall, so a little water resistance would be needed

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    Not directly relevant for OP, but there is a theoretical maximum length for a run of Ethernet cable. A copper Ethernet cable (or string of coupled cables) such as Cat6 will not work properly if it is longer than 100 meters because it will take too long for a signal to travel through the cable, interfering with the protocol's collision handling.
    – A. R.
    Aug 29, 2023 at 13:02
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    @MarcWilson what about the ethernet cable embedded in the wall, going through all kind of unknown crevices and popping out in a wall. How practical is it to redo that?
    – WoJ
    Aug 29, 2023 at 15:32
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    Terminate the cable, apply some dielectric grease, attach an Ethernet coupler, run a patch cable the rest of the way, and glob some hot glue over the entire coupler to prevent water intrusion.
    – MonkeyZeus
    Aug 29, 2023 at 18:05
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    Ethernet spec is 100 metres, not 100 feet. OP has plenty of capacity. I've even run some links out to 130 metres successfully (though not all network cards coped)
    – Criggie
    Aug 29, 2023 at 23:13
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    @A.R. Eh... that's a mix of truths and weird logic. Yes, the specification is to 100 meters, but the issue is attenuation, and causes 1s and 0s to appear too similar. Length can go longer when there is less interference, and much shorter if there is significant interference. It has nothing to do with collision handling, since Switches are standard network devices and you have to go out of your way to get an old-school broadcast Hub.
    – Nelson
    Aug 31, 2023 at 0:47

3 Answers 3

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Not what I'd do, but there's no such thing as a cable that isn't practical to redo in my world.

Waterproof ethernet coupler. They are commonly available. Assuming the case (unstated) is that you have a plug, it's a female to female coupler and a water-resistant housing that goes over the coupler, enclosing a short section of the cables leading to the coupler.

You'll also need an exterior-rated (water and sunlight resistant) patch cord.

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    To add to this answer: you will want to use quality light dielectric grease in these connections. Ethernet was never intended to be an outdoor connection, and keeping water out in a way that is reliable long-term takes some work. Thankfully the cable itself is usually surprisingly durable. I've used cheapest-available Ethernet cables for a decade+ before unprotected on rooftops. The cable is never a problem. It's always the ends that are trouble.
    – KMJ
    Aug 28, 2023 at 23:24
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    Make sure the patch cord is pure copper, not CCA scam junk. This is especially important for POE that carries power.
    – Thomas
    Aug 29, 2023 at 12:37
  • @KMJ: Meanwhile we use what looks like the extra durable kind of Ethernet cable on rooftops, but we keep ending up with link issues and occasional WOE (Water-over-Ethernet) every year :(
    – user1686
    Aug 29, 2023 at 13:49
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    @MSalters you have not read the question carefully. Note the last sentence.
    – Ecnerwal
    Aug 29, 2023 at 14:01
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    So you have a world where cables like this aren't typically plastered in, painted over with a paint no longer economically available, and barricaded behind furniture that would take hours to unload and reload with the stuff in/on it? Enviable! Aug 30, 2023 at 14:36
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Extend the wire while indoors with a coupler, and make sure that the section exposed to the outside is weather-proof.

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There are also weather-proof couplers available, but obviously at a higher cost:

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If you really don't care to re-use the coupler, I'm sure you can seal it up with any assortment of sealant or material available.

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Was it solid core or stranded core cable installed ? Solid is cheaper and easier to work with, but tends to break after a few months if subjected to movement so its ideal for inside walls and roofs.

If you have solid, I'd terminate it in a waterproof jack, and then use a stranded patch cord to go to the powered item. The stranded will be replaceable in the future.

If you have stranded cable running the whole distance, then I'd do the same BUT you will either need a jack designed to take stranded wire in its punchdown connections. Don't try and ferrule or solder all the strands together, that never works reliably.

If you can't find a waterproof jack. then shorten your 100 foot run so the joint will be in shelter. Also make a point to put the joint higher than the cables approaching the joint, so rainwater will drip off and not run along the cable into the joint.


Finally you can stop this kind of thing in the future by improving your method. Pull the cable(s) from the box(es) and through the building. Then terminate the far end. Leave a little slack cable in case you want to move things later.

When that's done, work your way back along the run securing the cable loosely. Don't use staples - I personally like cable/zip ties but formed into a wide loop or sling. There are few times where strapping cables together is a good idea.

Then and only then do you cut the cable to length. Again allow yourself a metre of slack. Many pro installers will bring cable into a cabinet in a nice loop, so the cabinet can be rolled/opened without undue strain.

Then terminate the patchpanel end into a jack, and test the run with a simple wiring tester.

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