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Old 10-08-2012, 12:05 PM   #1
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Underground conduit with underground LB


A couple of years ago, I ran a 20 foot underground run sch 40 with 12ga THWN. The run is under my lawn and goes from my house to a remote gfi outlet in my yard, the outlet box is bolted to a 4x4 riser. Here's my concern, I messed up and didn't allow enough wire to come up to the remote outlet, so I put in an LB directly under the outlet (about 18 inches underground) to connect another leg of THWN up to the outlet. I connected the wires with wire nuts and smeared a bead of silicon around the cover of the LB to help keep water out.

Is this okay and safe, or should I dig this up and run a new "unbroken" length of wire though the conduit and remove the LB?


Last edited by kevinf.; 10-08-2012 at 01:13 PM.
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Old 10-08-2012, 12:44 PM   #2
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Underground conduit with underground LB


If it is only a 20 foot run of 12 THWN inside of PVC conduit, it would not be too difficult to pull new wire.

I do not think that the PVC LB's, even with silicone, are made to be underground.

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Old 10-08-2012, 12:59 PM   #3
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Underground conduit with underground LB


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If it is only a 20 foot run of 12 THWN inside of PVC conduit, it would not be too difficult to pull new wire.

I do not think that the PVC LB's, even with silicone, are made to be underground.
You're right, it wouldn't be hard to do, just the cost of the new wires and my time and effort. But to my main concern, is the way I have it set up now unsafe? Even though it's not right, am I correct that it is not a safety hazard because it's a gfi outlet?
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Old 10-08-2012, 01:31 PM   #4
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Underground conduit with underground LB


A GFCI outlet protects what is downstream. Any thing plugged into it, and if wired as a load, the wiring and additional outlets beyond it. Your underground wiring is not GFCI protected by that outlet.

What type of wire nuts did you use ? Same as indoors ? Not an approved method.

If code is the minimum safety standard, anything less than code is unsafe.
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Old 10-08-2012, 01:33 PM   #5
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Underground conduit with underground LB


Odds are that you'll find that conduit full of water. Your connections are then in water.

Moisture does accumulate in conduit.

Was the LB marked as to it's volume? If not, you can't use it for your splices. In addition, you don't meet Code.

314.29 Boxes, Conduit Bodies, and Handhole Enclosures to Be Accessible. Boxes, conduit bodies, and handhole enclosures shall be installed so that the wiring contained in them can be rendered accessible without removing any part of the building or, in underground circuits, without excavating sidewalks, paving, earth, or other substance that is to be used to establish the finished grade.

Fix it.
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Old 10-08-2012, 01:42 PM   #6
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Underground conduit with underground LB


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A GFCI outlet protects what is downstream. Any thing plugged into it, and if wired as a load, the wiring and additional outlets beyond it. Your underground wiring is not GFCI protected by that outlet.

What type of wire nuts did you use ? Same as indoors ? Not an approved method.

If code is the minimum safety standard, anything less than code is unsafe.
Thanks. I used standard nuts used indoors. Pretty easy decision here, I'll just fix it, no big deal to do. Here's some more info, this is a switched circuit, so am I right that no harm can be done as long as it's switched off, until I can fix it right?
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Old 10-08-2012, 01:46 PM   #7
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Underground conduit with underground LB


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Odds are that you'll find that conduit full of water. Your connections are then in water.

Moisture does accumulate in conduit.

Was the LB marked as to it's volume? If not, you can't use it for your splices. In addition, you don't meet Code.

314.29 Boxes, Conduit Bodies, and Handhole Enclosures to Be Accessible. Boxes, conduit bodies, and handhole enclosures shall be installed so that the wiring contained in them can be rendered accessible without removing any part of the building or, in underground circuits, without excavating sidewalks, paving, earth, or other substance that is to be used to establish the finished grade.

Fix it.
Thanks! How can water get into the conduit if it's sealed (glued connections)? Does the moisture seep though the connections? If so, is there a way to prevent it?
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Old 10-08-2012, 02:07 PM   #8
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Underground conduit with underground LB


Underground conduit is a a wet location.
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Old 10-08-2012, 03:18 PM   #9
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Underground conduit with underground LB


Condensation eventually fills the conduit. Use electricians duct seal around the wires to seal both ends of the conduit.

Last edited by Glennsparky; 10-08-2012 at 03:22 PM.
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Old 10-08-2012, 03:51 PM   #10
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Underground conduit with underground LB


You can replace the LB with an underground junction box. The top would be just at or below the surface so your joints are accessible.
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Old 10-08-2012, 04:04 PM   #11
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Underground conduit is a a wet location.
Thanks. So for a different, but related question, would you recommend drilling small weep holes in above-ground junction and gang boxes? Or would this be unnecessary? I have several outdoor runs in my yard with outdoor covers and PVC junction boxes.
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Old 10-08-2012, 04:27 PM   #12
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Underground conduit with underground LB


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Originally Posted by kevinf. View Post
You're right, it wouldn't be hard to do, just the cost of the new wires and my time and effort. But to my main concern, is the way I have it set up now unsafe? Even though it's not right, am I correct that it is not a safety hazard because it's a gfi outlet?
unfortunately us professionals on the site will not tell you what you want to hear. Your best bet is to dig up the LB, extend the pipe up to your plug and pull new wire.
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Old 10-08-2012, 04:50 PM   #13
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Underground conduit with underground LB


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Originally Posted by kevinf. View Post
Thanks. So for a different, but related question, would you recommend drilling small weep holes in above-ground junction and gang boxes? Or would this be unnecessary? I have several outdoor runs in my yard with outdoor covers and PVC junction boxes.
I have done this, but it is not necessary.

I have opened old weather resistant boxes, holding the water in just fine.

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