which pipe should I use

v1rtu0s1tyOctober 18, 2010

I want to add lighting to my new patio. I want to add 2 pillars with lamp light on top of it. At my old place, I don't recall what the landscapers put. I think the depth of the pipe was 10" from the top of the patio floor.

I want to do it myself. I did some search and found out from an article to use high density polyethyline pvc.

Any help would be greatly appreciated.

Thanks.

Neil

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petey_racer

Electrical PVC conduit. The grey stuff.
Sch40 is fine for underground.
18" deep to the top of the conduit.

    Bookmark   October 18, 2010 at 9:58PM
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v1rtu0s1ty

Why do we need to go down 18"? Thanks so much!

    Bookmark   October 18, 2010 at 10:04PM
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petey_racer

You'll have to ask the code making panels this one. This has been the code for a very long time.

    Bookmark   October 18, 2010 at 11:00PM
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smithy123

use sch 80 pvc, 3/4''

    Bookmark   October 18, 2010 at 11:44PM
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v1rtu0s1ty

Thanks for the help everyone. I really appreciate it. :)

    Bookmark   October 18, 2010 at 11:50PM
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brickeyee

If you are willing to deal with intermediate or rigid conduit the burial depth goes down to only 6 inches.

It is much harder to work with (think threaded steel plumbing pipe).

    Bookmark   October 19, 2010 at 9:26AM
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v1rtu0s1ty

are this rigid conduit metal?

    Bookmark   October 19, 2010 at 11:47AM
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brickeyee

"are this rigid conduit metal?"

intermediate and rigid are steel with zinc plating.

    Bookmark   October 19, 2010 at 3:02PM
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v1rtu0s1ty

Thanks! I'll go with that one then. I don't want to go as deep as 18 inches since even at 10 inch deep, it is very hard to dig in my area.

    Bookmark   October 19, 2010 at 9:32PM
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smithy123

how do you watertight the threads? i always wondered that.

    Bookmark   October 19, 2010 at 10:14PM
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DavidR

You don't. Buried conduit is by definition a wet location. You expect it to fill with water eventually.

    Bookmark   October 19, 2010 at 10:59PM
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brickeyee

"how do you watertight the threads? i always wondered that."

The threads are IPT, the same as water pipes but no dope is required so the seal is not really water tight.

Condensation is going to very likely eventually fill the pipe up anyway.

Buries is a wet location and the correct wet rated wire is required.

Just about every buried conduit eventually ends up filled with water.

    Bookmark   October 20, 2010 at 8:26AM
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smithy123

is that why it is requireed to be arranged to drain?

    Bookmark   October 20, 2010 at 3:36PM
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brickeyee

"is that why it is requireed to be arranged to drain?"

No, that is why wet rated insulation is required.

    Bookmark   October 20, 2010 at 8:57PM
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Ron Natalie

Yah, I learned that on one of my first days on the job. We cut into a conduit feeding one of the buildings and water ran out of it for several minutes. My "older than electricity" supervisor made some crack about water cooled power conduits...

    Bookmark   October 21, 2010 at 8:14AM
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brickeyee

"We cut into a conduit feeding one of the buildings and water ran out of it for several minutes."

Count yourself lucky if it did not smell like dead animals and sewage.

    Bookmark   October 21, 2010 at 8:42AM
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smithy123

if the conduit fills with water, why do we use it? why don't we just direct bury the wire.

this link is where i thought all conduits must be arranged to drain.

Here is a link that might be useful: what's wrong here

    Bookmark   October 21, 2010 at 3:49PM
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v1rtu0s1ty

This is what I really want to put, pillar with lights. I had it at the old place. So what's the safe way to do this?

    Bookmark   October 21, 2010 at 4:49PM
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Ron Natalie

We use it because it's easier to pull wires in conduit that's in place than direct bury, you can place it closer to the surface, the wires are better protected against physical damage, you can't even get UF in a large enough sizes for some applications.

VIRTUOUSLY: The way I would do that is to run conduit up to a junction box mounted in the stone pillar where you want the receptacle and then another up to the base of the luminiere.

    Bookmark   October 21, 2010 at 5:16PM
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countryboymo

It should only be a dig once situation if long enough sweeps are used and it is built properly. If something happens the bad wire can be pulled out and a new wire pulled back in its place. Water will get in the pipe no matter how much pipe dope or glue you use..

    Bookmark   October 21, 2010 at 9:42PM
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v1rtu0s1ty

I remember the person installed a metal junction box beside our foundation. What is the use of junction box? Is it for ease of wire installation?

    Bookmark   October 22, 2010 at 1:32PM
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v1rtu0s1ty

he tapped it in our GFCI outlet outside. However, he did it via the basement.

    Bookmark   October 22, 2010 at 1:33PM
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smithy123

i would personally run a new 20a line from the panel.

    Bookmark   October 22, 2010 at 3:33PM
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brickeyee

"if the conduit fills with water, why do we use it? why don't we just direct bury the wire."

And what do you think happens in side the jacket of direct burial wire?

It slowly fills with water.

The is why UF does not have any paper filler that could cause problems, while NM is not allowed in wet locations because of the paper filler.

"this link is where i thought all conduits must be arranged to drain.

Here is a link that might be useful: what's wrong here"

You might try looking in the NEC for code requirements.

    Bookmark   October 22, 2010 at 3:35PM
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smithy123

"if the conduit fills with water, why do we use it? why don't we just direct bury the wire."
I meant to just bury the wire directly without conduit or uf cable. just the individual wires.

    Bookmark   October 23, 2010 at 1:09PM
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brickeyee

"I meant to just bury the wire directly without conduit or uf cable. just the individual wires."

Just a little mater of safety and the NEC not allowing it.

    Bookmark   October 23, 2010 at 2:22PM
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smithy123

if the conduit fills with water, why does the code require it?

    Bookmark   October 23, 2010 at 3:01PM
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petey_racer

Smithy, are you seriously asking why we cannot run individual conductors in the ground???

    Bookmark   October 24, 2010 at 8:44AM
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smithy123

no. im saying if the conduit fills with water, what is the point of using it. why are the codes there? WHY?

    Bookmark   October 24, 2010 at 9:03AM
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brickeyee

"no. im saying if the conduit fills with water, what is the point of using it. why are the codes there? WHY?"

For mechanical protection of the conductors and tier insulation from damage.

If the correct insulation is used the water does not have any effect.

Water is not actually a conductor at all, it is dissolved ionic contaminants in the water that conduct the current.
Very pure water is used as an insulator in electrical discharge machining.

The NEC rules are that conduit systems are sealed to prevent wholesale entry of water.

Buried system often eventually fill with water, but with the correct insulation on the conductors and the very low resistance of the wires themselves there is not significant current leakage.

    Bookmark   October 24, 2010 at 9:25AM
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smithy123

why dont we just use concrete?

    Bookmark   October 24, 2010 at 12:54PM
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kurto

Concrete doesn't conduct electricity very well.

    Bookmark   October 26, 2010 at 2:40PM
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smithy123

well, neither does ent. btw, does rigid count a a ground stake when running it underground from panel 2 panel?

    Bookmark   October 26, 2010 at 3:40PM
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