I am planning to pour a concrete patio. I would like to run two pieces of PVC conduit either UNDER the slab or IN the slab for future electrical lines. I would "cap" each end of the conduit until I find a need to run the lines. What is best? I am concerned that running the conduit under the slab (below grade) would allow water infiltration once I remove the "caps" and run the lines through the conduit. Would this be a problem? I could avoid water infiltration by placing them IN the slab (above grade), but this requires a little more preparation.

Any thoughts?

 

Yes, the conduit will absolutely fill up with water. There's no real way to prevent it no matter what you do. Even if no water enters the conduit, it will fill with water merely from the moisture that condenses out of the air that enters it.

But it doesn't matter. When you eventually put wire in that conduit, you will use a type of wire that won't mind being under water. There are a number of kinds that fit this description.

Don't forget to leave a rope in the conduit for later use pulling the wire.