4" drain pipe is dirt cheap, it holds a lot of wires and you do not need couplings. John KK9A From: "Gary Schafer" <garyschafer at largeriver.net> Date: Mon, 29 Jan 2018 12:08:37 -0600 (by the way 2 1/2 inch electrical conduit seems to be the best for the buck as 3" price jumps a lot) 73 Gary K4FMX