Twisted Pair Splicing: Should I Do It Or Not?

A student in IPVM's IP Network class asked if they should ever splice an ethernet cable? If so, how? If not, why?

What do you think?

In general, splicing should be avoided. Here's why I have this opinion:

1) Twist Rate: Remember the 'TP' part of UTP/STP is an important feature. The specific twist rate of a cable is sure to be disrupted at a splice point, and all the nasty performance impacts you're trying to avoid can creep up at that point.

2) Oxidization: All metal oxidizes when exposed to air. A conductive material like copper will have degraded performance when this oxidization occurs. In short: a splice may not cause performance/bandwidth/speed issues when freshly cut, but over time can disrupt performance.

Splicing, if done right (Hint: never use wirenuts like the image above) may not be a 'showstopper' causing gross malfunction, but it can present a significant bottleneck that should be avoided.

Am I missing others?

The specific twist rate of a cable is sure to be disrupted at a splice point...

Though with Wirenuts you can keep that twist rate right to the 'end'. Kidding.

If two separate cables need to be connected together (for example, to lengthen a short run) and a new single run is not possible, I would recommend putting jack on one cable and a plug on the other, then connect the two.

This will help keep the integrity of the twists and would serve as a 'better' option than using wire nuts.

As Brian mentions, it should be avoided where possible. But in reality sometimes it cannot be avoided. In these cases I feel the 'jack and plug' method is more appropriate than wire nuts.

Here is an example of a jack and a plug

Ideally, never do it.

That being said, not all situations are ideal. The instances in which I would not do it:

  1. Cables are being certified and documented, especially for bid projects. The splice will show in tests, generally speaking. Whether or not they're scrutinized that much varies per job, but I've known people who have been caught.
  2. When repulling it is relatively easy. If you can have another one in to replace the cable in an hour, repull it. Doing things right and fixing mistake is one of the things that separates a real company from a trunkslammer.

That being said, there is something in standards called a consolidation point. I used them in my cabling past in open offices. It's essentially a set of trunk cables pulled to one point, then terminated to a block and patched to another shorter set of cables which serve the area. They're shorter and normally intended to be repulled when offices are rearranged periodically, while the trunks remain in place.

A splice done correctly is really no different than a consolidation point, which is why I can be ok with it in emergencies. How I generally do it is to get a two port surface mount box, like so:

Terminate both ends of the splice to a jack of the type used in the rest of the installation, matching or exceeding the Category rating (Cat5e or 6 on a Cat5e system, Cat6 or 6a in a Cat6 system). Patch them using a factory terminated cable, at least 1' to maintain a decent bend radius.

There are also punchdown splices made for this, but I generally avoid them because they always seemed to be made by cheap no-name manufacturers, and I preferred to use rated components I trust.

This box should be located somewhere accessible. Mount it to a wall above the ceiling, attach it to building steel, etc.

Do not:

  • Hide the splice in a bundle somewhere for someone to find later. Techs everywhere hate you.
  • Use wirenuts or beans or 3M crimp connectors. At least try to maintain some semblence of category rating and professionalism.
  • Put a jack on one end and a plug on the other and tape them up. Theoretically, it's one fewer connection and should be a higher quality link than two jacks and a patch...but it'll come apart. Inevitably, believe me, it will come apart. And field-installed plugs are much harder to terminate well than jacks.

Man, I hate those gel filled beanie connectors.

They might work great in your alarm panel, but they have no place in an ethernet network.

Another option, is the Bicsi blessed, Emergency Ethernet Repair Kit

Just don't call it a splice, and you're good to go!

Where is the Bicsi stamp of approval on that product/idea? I have been looking and am unable to find anything.

Yeah, I concur. I see the BICSI logo on the cutsheet, but no endorsement anywhere, even on Metz Connect's webpage.

The 'Gospel' from the Director of Standards at Bicsi:

Dear [Undisclosed A], Thank you for the question.

BICSI does not officially endorse any product. We do repost presentations, such as the one presented in Singapore. We can also provide information to help aid in a decision.

The intent of the standard (both TIA and ISO) is to have a minimum amount of breaks in the horizontal cable. The wording used in TIA is more forceful in that there is to be no splices. This is where it get interesting. Some people feel a splice is anything that you use to connect to cables together that isn’t a plug/jack. Others feel that a splice is something you find in a splice case. In this case, the presentation leans towards the latter interpretation.

Regardless of the “word lawyering”, it is very bad practice to repair cables in the horizontal like this, as there is definitely be loss and potential other effects from the connector/splice. What is also not mentioned is what is the pass/fail rate of the cable after the item is installed, as cabling should be tested whenever there is a change to the permanent link. While there can be a time advantage in repairing a cable in this manner, it would require a specific set of circumstances where it would be faster than pulling a new cable in the horizontal.

As far as the other assertion about ease of transition, plenum is a code enforced item in the US and has a number of other requirements, including that non-cabling elements in the plenum space are required to be rated for plenum. Transition to OSP cable is also governed by code.

Now, as this product does exist, I believe I finally found the primary application to where something like this would be used – industrial automation. Industrial automation has many singular cables and are at increased risk of physical damage or being completely severed. As most cabling has minimal protection and is out in the open, said product (Specific for Class Fa/Cat 7a) would be a quick fix and not affect bandwidth, as industrial automation can survive easily on what Cat 3 providers. Any the presentation looks generic, it has an industrial, as direct connect (issue 2) is increasingly being used for static device/sensors utilized in many area, including industrial automation, and issue 3 focuses on the industrial Ethernet connectors. So, in 99% of situations/scenarios, standards and BICSI do not allow/recommend devices like these in the horizontal. For industrial settings, we could see where one might opt differently, as ultimately most standards are voluntary adoption, and can be ignored if one so chooses (unless otherwise specified by contract or other agreement).

Not knowing you exact application, I cannot go further, however if one chooses to use a device like this, it is heavily recommended to check with the cable manufacturer to see if the use will void the warranty of the cable.

If you have any further questions, please do not hesitate to ask.


Jeff Silveira, CAE, RITP, AStd Director of Standards

Heck of a guy, eh?

Thanks for sharing that, 'A'!

Where is the Bicsi stamp of approval on that product/idea?

Bottom right? ;).

Seriously, I think the technical exemption is based in the fact that it is essentially a single cable consolidation point.

Sorry, I forgot to include the link.

Sorry, but just because they put a Bicsi image on their power point doesn't mean it is Bicsi approved. It may be, but I have still yet to find proof of that. The link is helpful thank you for posting it. I agree with your comment, they are trying to re-define/water down the definition of a consolidation point to justify their splice product.

...but I have still yet to find proof of that.

What do you think you will find? Does Bicsi approve actual products by vendor part#? The PowerPoint was also on Bicsi's website. Finally I only said it was blessed by Bicsi, which is much less stringent a requirement... ;) is very bad practice to repair cables in the horizontal like this, as there is definitely be loss and potential other effects from the connector/splice. Jeff from Bicsi

Here's what I don't get: Does he mean even when the splice is done as well as possible, that there will be a significant loss/adverse effects seen at once? If it tests ok, is it ok? Or is the real problem down the road, due to oxidation, like Brian suggests?

The reason I ask is because it doesn't make sense to me why the splice would be any worse, signal wise, from a jack and plug, like Matt suggested.

But if the insertion loss from a jack and plug is significant, why does Bicsi generally recommend the extra jack/plug/patch camera side?

The jack/plug/patch camera side isn't "extra", it's part of the "channel", which is the full cable run, from switch, through patch cable, to patch panel, through installed cable, to jack, to patch cable, to device.

Jeff doesn't necessarily mean there will be significant loss/adverse effects seen at once. Most everyone who has been in the industry for any amount of time has spliced a cable. Circumstances come up and you do your best to avoid it, but it happens.

Oxidation may be a problem, yes. It's normal for pins of connectors to corrode over time. The problem is multiplied when you add a splice or another set of connectors to corrode over time.

I don't speak for BISCI but generally my opinion based on experience and working with others with substantial experience is that if it tests ok, yes, you've done the splice right. Whether that makes it "ok" isn't hard and fast, and depends on the environment of the job. I actually meant to mention testing as an absolute must in my original post up there but forgot.

The splice isn't necessarily worse than a jack/plug if components are rated and quality product, but a lot of the fear here stems from the fact that they generally aren't. There haven't been products available specifically suited to this, though that Metz splice is neat, so it's all new ground and I don't think the BICSI crowd is used to it and quite knows what to do with it. That's why he and others will generally not speak in hard and fast terms.

Plus, if you allow one splice, why not two? And if you've allowed two? Why not three? Why not as many as it takes to repair a chopped up cable? It's easier to make the determination of "don't splice" and recommend repulling cables, but take a break in cable on a case by case basis. As a standards making body, you have to have...standards.

That makes sense, thanks.

The jack/plug/patch camera side isn't "extra", it's part of the "channel", which is the full cable run, from switch, through patch cable, to patch panel, through installed cable, to jack, to patch cable, to device.

Curious, do you think those expensive cable certifiers would be able to detect the difference between a 'direct attach' plug and one that has the standard jack/plug/patch?

Standaards define 4 up to 6 connector Channel Models. Depending On the nummer of connections you allready have in Youri channel, the splice might be the one to many as standaards are concerned.

As Ethan mentioned, one is ok why not two etc etc? Because in the end you won't know how many you allready got in place. Unless you al guys document you're installaties better than 90% of all Cabling installers...which i honestly dear to doubt (forgive me my lack of confidence here ????)

Bottom line, if iT tests ok iT schold werk without problems sure enough. Ever tried to make à Cat.7(a) link fail on for instance a Fluke DTX1800 tester? I have and iT took me four knots in the cable, a desk On one of the knots and me jumping On iT several times before iT failed. Ok, the test passed with 'only' the knots in the Cable but i wouldn't want that in my installation.

So in my view, stick to the standards, test and...hope for the best

Surely it depends on the reasons driving the decision. As a permanent installation - of course not. As a temp fix during a late night service call - maybe. Plug and jack method would be the preferred route.