These are 2003 furnaces, not twinned, just in the same closet; one serves the first floor, the other the second floor. In the one pict, where the drain line is in the almost-vertical position, that's the "natural" position of the lines. I'm pretty sure the tops of these lines once connected to something that ain't there no more. They didn't connect to the bottoms of the inducers, though, where the yellow caps are; I know this for a couple reasons (even though I would think there would be drains there as well, as we see on lots of other furnaces).