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I am replacing flexible conduit buried slightly below the ground and attached to a septic tank with much stronger rigid PVC pipes. This conduit houses electrical cable.

I was planning on gluing all the joints in the "standard" way, but I have a significant concern that I won't be able to pull a replacement cable through the multiple tight bends I need to implement - and I know this cable will need to be replaced at some point.

Rather than gluing all the pipe joints my wife suggested taping them. I like this idea as it means I can unwrap the tape and separate the joints to run the new cable. I assume I would use electrical tape or something very similar.

Is this acceptable practice?

  • Help us understand the correlation between the flexible conduit you are replacing and the PVC lines for septic. How is the conduit attached or part of the septic and why? And "NO", electrical tape won't be sufficient. – HoneyDo Oct 20 at 18:40
  • @HoneyDo My take is OP is replacing flexible conduit with rigid PVC conduit. The conduit just goes to the septic tank, probably to supply power for pump and/or alarm. – PhilippNagel Oct 20 at 18:50
  • Why are you certain it need to be replaced in the future? Even if it was advisable (or legal) to do so, the tape would need to create a water proof seal and not decompose. – Alaska Man Oct 20 at 18:50
  • @HoneyDo The flexible conduit was used to connect pump servicing the drainage field, the aerator and septic tank switch. The conduit is connected with a metal clip bolted to the top if the (concrete) septic tank. Im replacing the flexible PVC with solid PVC as I am replacing a failed pump and could not pull the old cable out - and the flexible conduit was cracked and brittle. I want a much stronger pipe (im planning on using 25mm solid pipe in 35mm pipe) on the exposed areas (maybe all areas!) as I use a weed trimmer in the vicinity. – davidgo Oct 20 at 19:03
  • @AlaskaMan Aerator pumps have a lifespan of years - the current pump is fairly old and I expect will fail in the next 1-5 years. The cable runs from the aerator directly through this conduit to the switch - without a join/break – davidgo Oct 20 at 19:16
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This sounds like you don't know much about conduit, and you're proceeding anyway, which will produce a homebrew hatchet job. Don't do it. Follow Code, and skill up as needed.

PVC conduit must be buried with 18" of cover. If you don't want to dig that far, use Rigid Metal Conduit (RMC or IMC) which requires 6" of cover. Cover means dirt on top of pipe.

I don't really care if PVC is glued (Code disagrees). Water WILL get in. However, you'll want to glue it in the places where pulling forces will tend to pull it apart. The PVC needs to be stoutly anchored so pulling forces move the wire instead of move the conduit.

You must use outdoor rated wire for runs outdoors in conduit. Water WILL get in, can't be avoided; one outfit laid a conduit for a race-track in high ground (well above the water table). Sealed well, no rain, but the next day they pulled over a gallon of water out of the pipe. Condensation.

You are not allowed to use PVC water pipe for electrical, it must be PVC electrical conduit. They don't make tight bends for that, they only make broad sweeps and conduit bodies. ...That tells me the "the multiple tight bends I need to implement" refer to either plumbing elbows, or improper use of conduit bodies. I've seen somebody push a "pulling elbow" type conduit body into a corner, access panel facing the wall, because the person was unaware of the existence of either sweeps or LR conduit bodies, or the purpose of that access cover.

To repeat, conduit must be pullable! Don't build anything you can't pull wires into later!

You must assemble the entire conduit COMPLETE before pulling any wires into it. Needless to say, the cheesehead who faced the pulling elbow into the wall assembled the conduit around the wires. Had to redo all of it, and had to scrap expensive wire since it was glued. If that's your motivation for trying to avoid gluing, then reboot your thinking about how conduit works.

As far as pulling around "multiple tight bends", you are only allowed four 90 degree sweeps in between pulling points such as conduit bodies or junction boxes. You MUST make full use of pulling points; you cannot pull around their corners (that will shred the wire insulation). Further, all pulling point covers must be accessible at all times forever without removing any building finish or disassembling any part of the building. You are allowed to block them in with movable things like file cabinets, but not built-in cabinets.

If you are doing everything right and are still concerned with pulling forces being excessive, then I have several tips.

  • Use individual wires, NOT cable. A very common "conduit novice" move is to believe that the only type of electrical wire is cable, and therefore, try to chicken-choke cables down conduit. This is legal, but really, really hard.. and this difficulty is likely to fail the project and force them to bring in a real electrician with a truck full of pulling tools. Pros don't pull cables, they pull individual wires. Next time you're at a home store, find a spool of #12 stranded THHN. Wouldn't you rather pull four of those? :) Yeah :) Also, these individual wires take much smaller conduit - 6/3 UF requires 2" conduit, four THHN wires fit in 3/4" conduit.
  • Use stranded, not solid. All else being equal, #12 stranded THHN is much easier to pull than #12 solid THHN. Yes, it's a PitA to put on screw terminals; don't - pigtail it to solid.
  • Use fewer sweeps. Code requires no more than four 90 degree sweeps between pulling points. For novices I strongly recommend 1 or at most 2. (pretty much can't avoid 2 on an underground run).
  • Use bigger conduit. The same wire will pull easier in a larger conduit - i.e. don't push the limits of conduit fill. If you are forced into multiple sweeps underground, go extra bigger. Nobody ever wrote in here going "I need bigger feeder wires to my outbuilding, but my conduit has plenty of extra room. What do I do???"
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  • Would also add to the tips to use good quality pulling lube. Makes a huge difference in my experience. – PhilippNagel Oct 20 at 19:57
  • Thanks for your advice - there are useful things in this post. (The fittings I am using are all for outdoor electrical cabling, and have a maximum of 4 bends - unfortunately I don't think I can eliminate these.) After reading posts here I am going to put in a junction box to facilitate changing the pump. – davidgo Oct 20 at 20:04
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    @davidgo if you're stuck with that many bends underground, contemplate routes that use bends other than 90 degrees, that might ease the turning. Also consider a curved route where the pipe itself bends gently - this still adds into the 360 degree restriction but is much easier to pull than a stock 90. – Harper - Reinstate Monica Oct 20 at 20:08
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    @davidgo -- worse comes to worse, whack a handhole into the middle of the run to serve as an access point :) – ThreePhaseEel Oct 21 at 1:08
  • "You must assemble the entire conduit COMPLETE before pulling any wires into it." - So I can understand, why is this the case? Is this stated somewhere in the NEC? If so, where? – Tom Getzinger Oct 28 at 19:51
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First off, you're not allowed to assemble conduit around cable. It has to be a continuous run assembled to specs. You'd be surprised and how many bends you can pull through with stranded THHN wire when you need to replace it. If you know the cable is bad, you might want to think about replacing it now while you're doing all the rework. Just a thought.

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  • I'm not wanting to assemble conduit around cable - which is my problem. In the current design - which I expect was implemented by qualified tradies, when I need to replace the cable I am going to need to feed it through the conduit - which may be impossible if I can't separate the joins due to the sharp 90 degree bends that are somewhat unavoidable. – davidgo Oct 20 at 19:14
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    @davidgo Separating the joints like that is basically assembling around cable. A good solution is running the conduit into a splice pit or hand hole. – JACK Oct 20 at 19:22
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    The concept of a handhole (exterior junction box / pulling point) is an important one for exterior complicated runs. It's often "the right way to deal with unavoidable complexity" and often unknown to the uninitiated. Protip - get up into them with 45s rather than 90s whenever possible. – Ecnerwal Oct 20 at 21:50
  • yeah, avoid sharp bends, if you have access ot a heat gun or propane torch you can warm the conduit until it becomes like a rubber hose and form wide bends easily – Jasen Oct 21 at 19:20

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