Electrical PVC conduit expansion couplings
#7
I'm running some feeders between the house and new workshop. I buried the UG PVC conduit when we were finishing earthwork. I now need to make the connections up and into each building.

Buildings in this part of Texas are all slab on grade and our soils expand and shrink with the annual changes in moisture levels. Theoretically the conduit would move somewhat with the building, but there may still be a differential shifting.

I've seen these slip couplings at Lowes . This sounds like it would take care of any shifting issues. The problem I have is that I have never seen an actual installation where these were used. Not in any of the reading I've done, nor in any local installation I've seen. Also seems like they would introduce a potential leak point. They have double o-ring seals, but those will eventually dry out.

Just wondering if anyone's every seen these used or has a recommendation.
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#8
From the 360 degree view it appears each end of that piece is a slip fitting to be cemented to conduit. If so install it vertically so the half with the larger OD is the higher end. Water won't be able to penetrate then. The conduit coming down from the top will be glued in and water will just run down the outside. It can't run back up into the joint.
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#9
I have them in my attic carrying the wires to the solar collector. Pretty simple to install. I have no issues with moisture and do not care if the seals fail. In my case, its to provide expansion due to the high heat in our location.

Is there information on how expansive your soil is? Inches movement per foot or something. you building may move, but if the first three feet of soil are moving with it, its no problem.

Are you coming in beside the building(s) and then entering above grade? Or coming in inside? Either way, it might be good insurance to use the slip coupling. I might try to find out what contractors typically do in your area. We successfully ignore the issue here. Install them as suggested with the inner portion down so moisture has less change of entering and get on with life. Cheap insurance if you any doubt.
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#10
Check out this short video on YouTube

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Mike
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#11
They are just a tube in a tube. Glue it together and go on.

I'm glad you are putting it in. The clay in much of tax is very expansive. I have seen conduits break at joints in long runs. Have even seen several sewer lines break in houses. They will break just outside the house at the cleanout. Often the long pipe will and up pulling away from the house and there will be a gap in the coupling break. So any time you are working on your clean out dig up the line cut it and put a fernco in there to allow the pipe to move.

As to how much it moves... it varies allot depends on location soil composition rain fall drainage etc. I have seen concrete porches heave a few inches after a very heavy rain when the weather has been dry.
The soil types vary widely here even with in a square mile. Here we are the exception it's pure sand. The other side of the lake it's slab rock with a layer of rock hard clay on top.
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#12
Like the video shows is a great installation with a LB. I've only used them once and it was for 2 - 2" pvc conduits entering a large meter box mounted on the side of a building. They just stubbed up out of the ground and we're used as connectors directly below the box. How are you entering your house? It shouldn't really matter if they leak. All pvc conduit gets water in it.
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