1/2" copper water supply pipe as electrical conduit?

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Old 11-04-16, 07:06 PM
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1/2" copper water supply pipe as electrical conduit?

OK this is going to sound weird but here goes.

I need to extend a 20A circuit from one spot (point A) on an interior wall to another spot (point B) on the same wall, about 25' away, pass the living room and kitchen to the den. This wall is part of a hallway and is long.

My original plan is to run wires into the attic, and crawl up there in the moldy dusty tight space and try and run it across and drop it down. Would need to drill holes in the top plate in two spots.

I started to do this by opening up two holes in the sheetrock at points A and B, well...to my surprise, I see a run of 1/2" copper pipe from original construction in the 1950s, which has since been abandoned. That pipe is a straight horizontal run from "somewhere", past point A, through over a dozen wood stubs, to point B, then continues somewhere. I am sure the line has been abandoned (actually there are two lines one hot one cold). I have already cut the line at point A and B with a saw. It's confirmed to be abandoned, no water or moisture inside. It's also confirmed to run from A to B directly...I can blow air into the pipe at point A and someone can hear it at point B.

So...is there any reason I cannot use this pipe like an EMT conduit and forget about having to crawl into the attic?
 
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Old 11-04-16, 07:12 PM
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Not a chance. You don't know where it goes beyond these two points. It could branch up or down. I'd do it right just to keep from having to do it over again.
 
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Old 11-04-16, 07:38 PM
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I am using only the stretch from A to B. I am not concerned about the section before or after. It's already been cut at those points. There is no branch between A and B because I can slide the pipe horizontally for a good 10" before one end hits a stud and slide it the other way with no obstruction, if there is a branch in between it would not pass the sliding test.
 
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Old 11-04-16, 08:25 PM
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My original plan is to run wires into the attic, and crawl up there in the moldy dusty tight space and try and run it across and drop it down.
That is the way. Wear a mask if you are worried about dust.
Would need to drill holes in the top plate in two spots.
A lot easier now then it use to be. Try it in a 120 hot attic with nothing but a brace and bit you will know how easy it is now.
So...is there any reason I cannot use this pipe like an EMT conduit and forget about having to crawl into the attic?
The inside is not smoothed out for pulling wire. It can nick and abrade the insulation on the wire.
 

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Old 11-05-16, 06:58 AM
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That is the way. Wear a mask if you are worried about dust...
A lot easier now then it use to be. Try it in a 120 hot attic with nothing but a brace and bit you will know how easy it is now.
It is 120 in my attic I am down in Miami. It's suffocating hot. Last two weeks has been cool so it helps. It's going to be a real pain because the spot I need to put a hole through has may be 10" of head room I will have to be laying on my belly, with fiberglass insulation all over and yes with a mask and head lamp and sweat dripping down my eyes. I am not even sure the room I have I can fit a drill with the spade bit...unless I get a flex bit to do it from below...is there a super long flex bit that can drill a hole from below (18" up from floor) through the middle plate, then through the top plate? I would have to open more of the wall. arghhh.
 
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Old 11-05-16, 09:10 AM
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The copper pipe is not listed for use as electrical conduit. That is a HUGE mark against it in my book. Further, both the inside diameter and outside diameter of 1/2 inch copper pipe is significantly smaller than that of EMT so where would you even get the end fittings necessary to connect the copper to a box or other conduit fitting?

As I recall this entire house is using conduit. Is non-metallic cable allowed? You cannot run individual wires (THHN/THWN) outside of conduit.
 
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Old 11-05-16, 09:55 AM
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I would push, pull, suck or blow a pull string or pull wire through pipe. After pull string is through I would than work copper out of wall. Copper will bend fairly easy so you should be able to get it out. Leave string behind as you pull pipe or just pull it out with copper. After pipe is out than pull your cable through holes. Make sure the string is lond enough so you won't lose it in wall.
 
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Old 11-05-16, 10:17 AM
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Pugsl, Great idea.
 
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Old 11-05-16, 12:38 PM
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As I recall this entire house is using conduit. Is non-metallic cable allowed? You cannot run individual wires (THHN/THWN) outside of conduit.
Yes house is all EMT (90%), there are some MC cables in the attic where the EMT runs from boxes in wall cavity up into an attic to a central junction box, then from that box it runs MC cables to individual recessed can lights.

I have been using EMT as I repaired/renovate basically to keep the same "style" not because of any code mandate. I am doing the same for plumbing it's all copper pipes so I kept it in copper so I don't run into a hodge podge of copper/pex/cpvc all over the place. Also with all EMTs I can use the conduit as EGC. Once I mix in NM-b and plastic boxes I lose the continuity.

But in the end I am not going to use the copper pipe because it's just a hazard for a future owner who may not know whats going on and open up a hole in the wall between A and B thinking it's water line and cut with a saw into live conductors.

I think in this case I will break my rule and use NM-b between A and B. I can feed a steel fish tape through the copper pipe from A to B. Once I see the tip of the fish tape at B, I can slide the copper pipe out as far as I can, then use a tubing cutter to cut the pipe without cutting into the fish tape. Remove the short cut section. Then slide another section out, repeat until the entire copper pipe is out. Then pull a 12-2 NM-b wire through. It should work.
 
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Old 11-05-16, 12:44 PM
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Sounds good. .
 
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Old 11-05-16, 12:46 PM
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Further, both the inside diameter and outside diameter of 1/2 inch copper pipe is significantly smaller than that of EMT so where would you even get the end fittings necessary to connect the copper to a box or other conduit fitting?
Well since I won't be doing it this is kind of moot now, but for the sake of the discussion the OD of a EMT is 0.706" and the OD of a 1/2" copper pipe is 0.625" so we are talking about a 0.07" difference. So I think just a regular 1/2" set screw coupling with another turn on the set screw should work to connect it to a real EMT conduit. Another option is to solder on a 1/2" copper female adapter to the copper pipe, and that 1/2" female thread should thread onto the male threads of a 1/2" EMT set screw box connector. The connection should work "in appearance", now I don't think the inside of these would provide a same I.D. smooth path so.
 
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Old 11-07-16, 02:21 PM
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I'm sure it would work just fine, but code does not allow it. Only listed electrical conduits and fittings may be used as such. At least we know copper pipe is smooth inside assuming it was deburred by the original installer, otherwise it could have a very sharp edge where the coupling was sweated in.

Too bad it wasn't 3/4 copper as that would be just about perfect to pull MC through and you wouldn't have to be concerned with it as a conduit.
 
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