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I am trying to pull four #8 stranded wires through a flexible PVC conduit that is 25 feet long. I can get the wires just a few feet into the conduit before they bind. I know there is a commercially available wire lube, but I do not have any. Can I safely substitute another product like dish soap or something? Or would that just be a bad idea and I should just get the real deal?

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    only a few feet? are you sure there's not another problem? – Steven Jun 2 '14 at 1:50
  • I pulled/pushed 100+ft of #10x3 wires through 3/4" without using anything for about 50% of the way. Towards the end I started using some dish soap and it went through pretty easily – Joe Phillips Nov 27 '17 at 18:15
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I'd agree with the comment that you may have another problem.

What size is the conduit?

Are you pulling or pushing (pulling is what works, pushing won't.) If you need something to pull with, use a shop-vac to get a rope through the conduit first. Braided hollow rope can be nice as you can expand the end and use it like a Chinese finger cuff to grab the ends of the wires (use tape as well.)

If the conduit is exterior and the wires are correctly rated for exterior conduit, you could use water as a lubricant. It's not a good idea to come up with a random soapy product, since the commercial products are tested for long-term compatibility with wire jacket material, some lube will remain in the conduit, and the wires are generally expected to be there for decades - over which time it's possible that the seemingly innocuous dish soap might have a deteriorating effect on the wire insulation, due to some component inconsequential in washing dishes (say, for example, the scent...)

The real deal is quite affordable if you can find it in quarts, which you generally can at most electric supply houses or the internet if you have difficult electric supply houses and your home improvement stores don't stock it.

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    That is what I was thinking, but I just wanted to confirm it. The conduit is the flexible PVC and is offering up quite a bit of friction, even at 3/4". I will get the real lube just to be safe. Thanks. – Posted by another Tim Jun 2 '14 at 2:43
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    Good Answer, And i totally agree about the shopvac and use of water, I did however use soapy water, and it did help. the pull action is the best, but if you have a friend that can help, its worth both pushing and pulling at once. – Hightower Jun 2 '14 at 13:14
  • Dawn dish soap is a great pull lube the only problem is it drys out after a while and trying to pull the wires out at a later date is almost impossible, but this also happened with commercial lubes, they do make non drying lubes, but in a residential I usually save a few bucks as these are not pulled as often as commercial or industrial. – Ed Beal Nov 27 '17 at 14:50
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The nominal diameter of #8 stranded copper with insulation is just over .21 inches. You are trying to pull 4 of these wires through 3/4 inch pipe. I'll bet the 4 wires together have a diameter of .5 inches (in the best case where the wires are still straight and have no bends.) That's a tight fit over 25 feet. I don't know if you are using a mechanical pulling device, but that would be very helpful if one is at hand.

It is pointless to try to push the wires that far. It would be like a shovel with a rope handle. As suggested before. Send a pulling rope down the conduit and attach it to the wires solidly. The trick suggested of using a rope like a Chinese finger puzzle is a good one. As for friction. A quart of the real pulling compound costs about 6 bucks and you will have plenty left for your next job. I agree that using dish soap is not a good idea. The insulting materials vary and the stuff will be in place for decades. Pinholes in the insulating material are a very real possibility and copper will start to corrode with soap. It's not likely there would be enough to degrade #8 wire, but why chance it.

Also, soap solution does not have as low a coefficient of friction as the pulling compound. After paying what you had to buy that amount of copper wire, spending the six bucks for a quart of the right stuff is chump change.

  • FYI The finger puzzle thing is called a pull sock. – Ed Beal Nov 27 '17 at 14:52
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In regards to the ANSI/NFPA 70 National Electric Code (NEC) is your flexible PVC referring to

  • Article 356 Liquidtight Flexible Nonmetallic Conduit (LFMC), aka smooth walled Sealtight or
  • Article 362 Electrical Nonmetallic Tubing (ENT), aka corrugated "Smurf Tube"

The link to the Elliott Electric Conduit Fill Chart only addresses metal conduit: RMC, IMC and EMT. Not PVC.

You need to look at Tables C2, C5 or C6 in the NEC to find what is legal for your wire type and flexible PVC conduit/tubing type. However, in all likelihood, unless you're using some thick 2-hour fire rated RHH, you are allowed, by code, to install 4ea THHN/THWN insulation, 8-AWG wires in 3/4" "flexible PVC".

Run a fish tape and pull line through your conduit/tubing (especially if smurf tube), then pull your bundle of wire through, making sure you wrap the head well with electrician tape so no bare wire sharp edges dig into your pipe. You shouldn't need lube if your conduit is straight. If you have more than 360 degrees of bends total, by code, you need to add a pull box or junction box.

If you have a kink in the conduit with an angle greater than 90 degrees or a tear or rip, or drywallers put a few screws into it, or someone mangled it with a forklift, decreasing pull resistance with lube probably won't solve your problem.

Stranded wire is easier to pull through bends than solid.

  • Pushing in flex is tough but can be done if there are only a couple of bends tape the ends of the wire tightly so that the tape is stretched and beyond the end of the wires. If it dosent go quickly blow or vacuum a string into the conduit have 1 person push the wire with a light pull on the string and you would be amazed how easy it will go. – Ed Beal Nov 27 '17 at 14:58
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Talk about code violations. This is way past the allowed fill rate for a 3/4 piece of conduit. The minimum conduit size for 4 #8's is 1.0, with a 75% fill or 1.5in with a 50% fill rate. That is so the cables can dissipate heat. Yikes! Hope your conduit/house hasn't burned down yet.

  • Do you have a source for that? All the conduit fill tables I've looked at say 3/4" conduit can take 6 #8s. e.g., elliottelectric.com/StaticPages/ElectricalReferences/… – littleturtle Apr 29 '17 at 3:53
  • @littleturtle It all depends on the type of #8 you specify. THHW normal conductor will let you have 4 in Schedule 40 3/4". It jumps to 7 in Sch. 40 1". Source is 2017 NEC Informative Annex C Tables (after Chapter 9). – Bill N Jul 12 at 17:15

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