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

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

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

use sch 80 pvc, 3/4''

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

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).

are this rigid conduit metal?

"are this rigid conduit metal?"

intermediate and rigid are steel with zinc plating.

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.

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

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

"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.

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

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

No, that is why wet rated insulation is required.

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...

"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.

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

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?

{{!gwi}}

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.

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..

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?

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

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

"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.

"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.

"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.

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

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

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

"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.

why dont we just use concrete?

Concrete doesn't conduct electricity very well.

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