I hate to disagree with you, but right in the directions it states that you may extend the concentric vent to a max of 60". You cannot use couplings and different size pipe. It must be one piece of SDR-26 both inside and out. My unit is not glued yet allowing for extension as well as shortening in a horizontal installation.
Last edited by 2480fool; 02-13-2011 at 07:39 AM.
Reason: forgot information