The main consideration that I'm aware of(besides weight, and Code requirements) for steel (Fe) v. Al is atmospheric considerations. Are there vapors which would affect Fe v. Al, or vice versa? If there are no atmospheric concerns, I guess it boils down to personal preference (As well as the AHJ, of course
I remember years ago seeing Fe, PVC, CPVC, Al, Stainless Fe, and some sort of bronze alloy conduit. Where there's a market, I guess...
[This message has been edited by DougW (edited 12-22-2003).]