I was wondering, can you even use Romex cable inside of outdoor PVC conduit, for outdoor applications? Its for the lighting for the backyard. Once I get my electrician's licence as a apprentice to a journeyman.

I was wondering, can you even use Romex cable inside of outdoor PVC conduit, for outdoor applications? Its for the lighting for the backyard. Once I get my electrician's licence as a apprentice to a journeyman.

According to the NEC, no...it's not legal.

No, it would need to be UF type cable to run underground and wouldn't need a conduit if it's direct bury.

Ok, thanks.

Lowes has UF type wire, and they're expensive for a roll.

Do you also have to use PVC conduit when not buried?

https://www.lowes.com/pd/Southwire-100-ft-12-AWG-2-UF-Wire-By-the-Roll/1000131815

I wonder if you can use 12 AWG for 20A circuits?

https://www.lowes.com/pd/Southwire-100-ft-12-AWG-2-UF-Wire-By-the-Roll/1000131815

I wonder if you can use 12 AWG for 20A circuits?

According to the NEC, #12 AWG is indeed rated for 20 Amps.

Using conduit is a problem if you live in a climate where freezing temps occur. If the conduit have sections running low and is not all inclined or have drain holes, it will eventually fill up with Water. When the Water freezes, it will put stress on the cable. Some cables may be suitable to withstand that sort of stress, and some not

In the places where the cable runs in the open, a conduit does help protect it from accidental mechanical damage. In vertical runs where the conduit is only starting above Earth level, there is none of the Water problem

When choosing the cable type, check that it is suitable to :

 - The temperature range, from low (at significantly low temps, PVC itself can freeze and get damaged, but this happens only further up North), to high (especially when under the Sun, including inside metal conduits and boxes that are under the Sun

 - The UV stability. Some cables are UV stabilized and some are not. Protecting the above Earth level parts with conduit helps preserve the cable even if UV stabilized (they aren't always fully UV proof)

 - Any mechanical loads, like if you want to suspend the cable, that it can carry its own weight

 - Its resistance to damage by termites, etc

Also, if you are going to load it continuously and there are sections subject to high temps, take higher margins from its max ampacity

I have  use standard romex in conduit  for years
Underground. Heck  u can even use 3 pieces of THHN
In conduit under ground. 
It all  depends on athority of jurorection
Meaning  u can ask your inspector what  min
U can get away with. 

A home owner can wire there own home even install
A steptic tank as long u  comply with inspector that issuing
U  permit

Nah, I'll use that UF-B wire, because its code compliant for outside, plus you can put it underground and burry it.

The big problem with using NM-B outdoors (in conduit or not) is that the paper liners can wick moisture.  UF-B uses solid plastic instead, so the moisture wicking isn't an issue.  However, this makes it more expensive and difficult to work with.  UF-B can be run in conduit, though it's not necessary where buried.