buried rigid conduit

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Bowhunter

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Are there any occasions that would allow rigid metal conduit to be buried 6 inches under ground on a residential job? Other than the notes at the bottom of Table 300.5
 
Take a look at column two in table 300.5. Unless you are running the rigid metal conduit under a street or a driveway, 6" is ok.
 
6" is okay but watch out for the drive way or designated parking for that residence must be 18" col 2 and 12" col 4
dick
 
So on a residential application such as to a swimming pool or a garage, the trench only has to be 6 inches deep unless I'm going under a driveway or parking area. If I use Rigid Metal Conduit?

Bowhunter
 
I recently re-fed a detached garage sub-panel behind a house. (approx. 50' ditch) The old, lead-covered cable finally gave out after about 75 years! I instructed the homeowner as to how deep he will need to dig the ditch. He called to tell me that his neighbor's electrician, many years ago, ran RMC underground to his pool equipment and it only needed to be 6" deep. I told him that was true, but I don't have a pipe threader and with all the bending and threading involved, it will cost a lot less to use PVC as I had priced. He agreed and dug an 18" deep ditch.
 
e57 said:
How do you keep water out of any conduit? For that matter - how do you let it out???? ;)
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With PVC you hope that you can seal the pipe with glue. But doesn't rigid use threaded rigid couplings? Just seems like the water can fill the pipe easily.

I don't know, I almost NEVER use rigid.
 
jaylectricity said:
With PVC you hope that you can seal the pipe with glue. But doesn't rigid use threaded rigid couplings? Just seems like the water can fill the pipe easily.

I don't know, I almost NEVER use rigid.
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Water in conduit is from condensation and not seepage from ground water. All buried conduit that I have ever demo'ed or re-pulled through has had water in it. That's the purpose for using THWN, and the like.
 
jaylectricity said:
With PVC you hope that you can seal the pipe with glue. But doesn't rigid use threaded rigid couplings? Just seems like the water can fill the pipe easily.

I don't know, I almost NEVER use rigid.
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Not sure of the code implications - but with some pipe dope - you could make it gas tight....

Anyway for some reason - well I can think of a few - but water always seems to find its way into PVC or RMC. If anything from condensation over time... But PVC glue - unless you're using the plumbing type with primer on un-oxidized conduit - seems to loosen in the presence of moisture. Even if you give it a few twists while setting to really lock it up... Seems to work best when you take a little sandpaper to the sun-bleached ends - locks up good after that.

As for RMC - I'll admit I doped a few. Only in special occassions, but like any other conduit - I expect a bit of water in it... Sometimes to keep the water in.... ;)
 
e57 said:
Not sure of the code implications - but with some pipe dope - you could make it gas tight....
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I would doubt that pipe dope would give you that tight of a seal. I think you would need to switch the conduit couplings with plumbing pipe couplings to do that.
 
Water in conduit

Water in conduit

I've seen a detail showing the conduit with holes drilled in the bottom at a gravel sump, with conduits sloped down to that point. I can't imagine that maintains the listing requirements, but it is an interesting approach when you don't have a manhole to drain to.
 
IslandSparky said:
I've seen a detail showing the conduit with holes drilled in the bottom at a gravel sump, with conduits sloped down to that point. I can't imagine that maintains the listing requirements, but it is an interesting approach when you don't have a manhole to drain to.
Click to expand...

If drilling a hole in RMC is a problem than so is bending, threading and cutting it.
 
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