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We're rural and the house plumbing is from a lake-draw system with a submersible pump.

We just noticed that the power wire out to the pump had its sheath damaged in the spring time by either the ice going out, or driftwood in a storm, or something. The inner wires are not damaged. That spot will be under water in the spring.

Underwater wire was ripped open through abrasion

The question is: how to patch it?

The submersible pump is far enough out that pulling it up and re-wiring it is a huge job (not to mention digging up the lawn).

We're hoping for a solution involving heat shrink, electrical tape, maybe clamping some PVC around the outside, etc.

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    The inner wires are damaged. The black wire is certainly not in the condition it was from the factory. The insulation may not be completely broken, but it’s not original.
    – nobody
    Sep 28 at 0:12
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    I can't talk to the details of your repair, but being rural you need stuff to just-work so there's a lot of merit to "do it once, do it right" despite the pain. Consider your urgent water needs if something's on fire for example. Do be grumpy at whoever installed this with insufficient protection originally, and make sure future-you is happy with your work. Remember this happened once, it could happen again.
    – Criggie
    Sep 29 at 1:30

5 Answers 5

34

Look for an underwater cable splice kit (standard listed product) and just use the outer encapsulating part of the kit, if the inner conductors are not damaged. The splice kit fill (an insulating material) will take care of any local insulation damage inside the splice kit shell if you ensure that wires are separated where damaged before filling. Usually a mold that clamps around the cable jacket and gets filled with an epoxy or epoxy-like (perhaps more rubbery than stiff) substance to seal the deal after the splicing is done.

You may want to carefully cut away a bit more of the jacket and clean all that sand out of there first. You may also opt to cut out a few feet of damage and actually splice, or more than a few feet & splice twice to insert a new section of cable.

When you get to redoing it right, install conduit (no more digging up the lawn after that, and more protection from damage.)

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    Most of the splice kits I am aware of have a need to slip a jacket or sheath up on the ends of the wires to be spliced. It would be a problem using such kit if the existing wires were not cut as would be the case for an actual splice.
    – Michael Karas
    Sep 27 at 21:06
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    The type of kit I'm referencing has a two-part mold that snaps together around the cable, and is then filled with sealant/insulation. e.g. 3m.com/3M/en_US/p/d/b10076896 The wraparound mold included in the kit allows you to repair the jacket without cutting through the cable. (Direct quote.)
    – Ecnerwal
    Sep 27 at 21:33
  • I used this one: amazon.co.uk/Resin-Underground-Armoured-Cable-1-5mm-10mm/dp/… last year, and it was easy to use, and worked perfectly.
    – emrys57
    Sep 28 at 9:47
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    Definitely clean all the sand out before calling it done. Debris inside the jacket can wear away the wires' insulation over time and cause a short or worse. Split the outer jacket open, find the farthest point in both directions that the sand has infiltrated, and cut the wire a foot beyond that.
    – bta
    Sep 28 at 16:31
  • These work well IME. 30 years ago we did something that I DO NOT RECOMMEND. Did not know better at the time. We had underground power to an outbuilding was which was cut. We used regular wirenuts, stuck the splice in a whole tube of silicone that we had cut the end off of and let it dry out before re-burying the line. Still working fine to this day, but that's luck, not skill. Sep 28 at 20:06
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I doubt that can be easily and safely repaired. Water and contaminants have infiltrated the outer protective cover, which will wick quite a distance into the outer cover. In addition, that black line does look like its own insulation has been compromised.

Without knowing the specifics of what you're dealing with, I'm thinking that you'll need to, at a minimum, pull out any line that's been underwater or contaminated all the way to the pump. Then put a suitable weatherproof junction box (above ground, most likely) near the waterline where you can connect the new pump's line to what's buried coming from your house.

Unfortunately, this means you'd need to pull out the water line as well, but I'm not seeing any other safe option for you.

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    If it's proper submersible cable, it should be full of either grease (more or less - a strongly hydrophobic greasy material that is safe for wire insulation and difficult to get off your hands) or a dry gel that swells on exposure to water, which limits the ability of water to get into and move along the cable when the jacket is damaged, Either would contribute to the demonstrated tendency for sand to stick to the open wound.
    – Ecnerwal
    Sep 27 at 0:56
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    While I think @Ecnerwal's answer addresses the damage itself, I do think that putting a weatherproof (specifically one that's rated for weatherproofness IN-USE) junction box out there is a good idea. Sacrifice the lawn even and put in a conduit while you're doing it, and future proof this. HOWEVER be sure the conduit and junction box are sealed and mounted at above flood level!
    – Doktor J
    Sep 27 at 14:17
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    @DoktorJ yeah, flooding this year was INTENSE. The wire goes underground at the bottom of a 14 foot retaining wall. High-water this year was halfway up the wall. Putting in a junction box above high-water will likely require digging out the retaining wall. Also, this spot can only be accessed by heavy machinery by water barge. $50,000 dig, or $100 kit and some hope. I'll go with the latter. Sep 29 at 0:29
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I'm going to add something to Milwrdfan's answer, in that I agree the cable should be replaced.

That's not UF cable, and looks curiously like NM cable, in that it seems to have a simple jacket (UF isolates all three wires in a poured nylon sheath). You've lost a good inch out of it at least. You've also demonstrated why not even UF cable is suitable for this application

Underground rating presumes physical protection by the surrounding earth.

It also sounds like this cable is fully exposed part of the year by a receding water line. You're lucky it didn't take more damage or you might be talking hospital bills. A splice is a mere band-aid for the problem (almost literally) and you're rolling the dice just fixing this one spot.

A while ago we had an excellent question about how you run wires underwater and I'll quote ThreePhaseEel

We will be using LFNC by the spool for a long run, or at least the longest coils you can get, here, to minimize the number of couplings to act as potential leak points.

And myself

What looks like a good pick here would be the newer XHHW-2 wire.

You could also go stainless steel conduit as well, but it's probably far more expensive and difficult to work with. In either case, you would avoid needing to splice cables underwater, and you would avoid any further damage.

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I would use self-sealing rubber tape. The ground wire has been wet, so may begin to corrode. If possible, a hairdryer or heatgun could disperse water before you seal it back. Whatever you do should buy you some time.

https://www.amazon.com/3M-Temflex-Rubber-Splicing-Tape/dp/B005298APQ

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  • You may be able to find an emergency plumbing repair kit - these usually consist of special "self amalgamating tape" that would be ideal. Whether the cable itself is okay is debatable.
    – MikeB
    Sep 28 at 15:00
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You can wrap it with electrical tape, and then apply pvc cement to melt/rebond the tape into a shell. https://99mpg.com/mikestips/blacktape/

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