What is the difference between above grade & below grade conduit ?

First, do you understand what the word "grade" means?


If you did, you would realize that below grade means underground, and above grade means above ground.

First, do you understand what the word "grade" means?


If you did, you would realize that below grade means underground, and above grade means above ground.

I think he's asking if you need special conduit for underground.

Depends on what you are trying to do. What is the application? Are you going under a driveway or road?

"grade" as used in this context refers to ground level, finish grade is ground level after all site preparation work is finished.

Conduit suitable for burial needs to be "listed" for that use, Rigid Nonmetallic Conduit is plastic and is used most often in residential applications. It is exactly the same material and wall thickness as Schedule 40 water pipe which is white, PVC conduit is grey to distinguish it from water pipe, water pipe is not "listed" for use as conduit, as conduit is not listed for use as water pipe.
Rigid Metal Conduit (RMC) is also suitable for underground use, it is metal and will take a lot more physical abuse but is much more expensive and labor intensive to install. RMC may not hold up as well as PVC under certain soils though. Both are acceptable for embedment in concrete although RMC may require a wrap of 10 mil PVC tape to protect it from corrosive effects of the concrete

This is not all there is to know about conduit suitable for use underground, If you need help with a particular project, we will need a little more detail about it