Hello everyone, looking around and some very informative info here. I have one question so far, Do I really have to use the expensive twist lock pipes? I know they are recommended probably for a reason but wow!! they are expensive!! Just asking. I intend on using a brick chimney that also has a fuel oil furnace using it. But of course one at a time. Any help please. I will continue to look around on the forum might find the same question answered.