GI Conduits

A major issue in some areas is corrosion of embedded metal conduit- cases I am familiar with involve the use of beach sand in the concrete mix. Corrosion of the steel conduit resulting from contact with the salt can result in damage to the concrete due to expansion resulting from the corrosion. Don't believe the contractor when he assures you he has washed the sand! If you are near the ocean, your sand most likely is going to have salt in it.

On the other hand, I have never encountered a problem with PVC conduit in concrete. I have drawn new wire into old PVC conduit with no problem- where in similar situations, the metal conduit must be abandoned.

PVC is used extensively during recent years due to its easy in handling it.

Cast my vote for PVC but no matter what you like it's always up to code.

In an industrial application, it is my company's practice to "mix" the 2 types of conduit.

We run PVC through the concrete, for ease of installation, but we transition to Rigid Pipe when exiting the concrete slab. In the past, we have seen PVC conduit damaged or even sheared off at the floor level by fork-lifts or other mechanical damage. For this reason, we currently use a pvc threaded female adapter ("FA") to change to a 90 degree rigid "sweep".

I am seeing more and more engineer's drawings specifying this method also.

Putting GI conduits inside RC concrete does not seem practical anyway especially for high humidity environment. The water vapor will condense inside the conduit wall and the small space between the conduit and concrete. As a result, sooner or later, GI conduit will be rust for such application. Have you ever checked the steel box? I prefer PVC in this case.