Conduit may be rusted shut?

Old 02-02-15, 05:09 PM
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Conduit may be rusted shut?

I have a 60s house where all the raceways are in EMT conduits, due to a flat roof, most of the runs are below, through a monolithic concrete slab about 4" thick.

I am trying to add a 120V receptacle in the closet, where there is an existing junction box for the 240V water heater. I opened the junction box and saw two solid #12 conductors, thinking I should be able to pass two more #12 conductors through (one hot one neutral), I fish tried pushing a steel fish tape in, and no luck, about 4-5' in it's stuck.

Now I am not that surprised, I usually don't have much luck pushing or pulling new conductors if the existing are sold conductors. So I was thinking, may be I will pull one of the conductors out first, then use the remaining one to pull 4 new stranded in.

It was VERY difficult to pull one solid #12 out. Much harder than it should. Once I got it out I knew I am in trouble. Here is a picture of the conductor.

The entire run is only about 25', 5' down, 15' across, then 5' up to the panel. There is a long stretch I can see rust on the insulation.

I am guessing the EMT conduit has corroded?

After this I decided I should pull out the remaining solid conductor out. I don't think I could have used it to pull stranded, it was really difficult to pull it out, and it too has this rust all over.

Then I tried my steel fish tape again, and again 5' in, no more. I am guessing that it is corroded to the point it will not even pass a steel fish tape?

My thinking is I am out of luck and I need to be thinking of creating a new route between the panel and the hot water heater and abandon this run of EMT...or is there any way I can still find a way to pull 4 new stranded through? The rust feel dry, not wet.
Old 02-02-15, 11:36 PM
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Your water heater should be using #10 conductors. The wires were tight coming out.... the snake wouldn't go thru. It really doesn't matter what happened to the conduit..... it appears to be no longer useful.
Old 02-03-15, 03:25 AM
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And starting at the roof, going down and back up, it is probably full of water, so rust is a given.
Old 02-03-15, 05:12 AM
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The EMT conduit is 50 plus years old and most likely runs not only through the concrete slab, but probably under the slab in some places as well. Yes, it is rusted beyond being able to be reused. This is precisely why PVC conduit is used today.
Old 02-03-15, 05:56 AM
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You can try to rehab the old pipe, but odds are it will be a lot of work without success especially if it goes underground. If it goes underground the pipe has almost certainly collapsed and cannot be reused. Through an above-ground slab -- maybe.

If you do want to give it a shot, put a shop vac on one end, secured really well with duct tape, and blow compressed air into the other end. This might loosen up some of the accumulated crap that's blocking the pipe. It can also make a colossal mess if that crap comes shooting back out the pipe into your room and face, so put up some drop cloths and at least wear glasses and a face mask. Alternate between the steel tape and compressed air and you might be able to clear it up.

If you can get the steel tape to pass through, use it to pull a rag back through a couple times to clean up what the air/vac didn't get. There are also bristle conduit cleaners you can pull through which sort of looks like a bottle brush with a pull hook. In fact for half inch pipe a bottle brush might be perfect instead of buying a speciality tool.

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