If you did no glue on any of the white stuff, you were not the biggest sinner.
The white piping isn't mine, with the exception of what I think is a reducer adapter that fit rather snugly into the larger white pipe. I think all of the rest of the white pipe is glued, although I did not dare torque it much to test it. For the white reducer I put in that came with the kit, I put some blue monster "pipe dope" around it which seemed reasonable.
I don't quite follow, and the picture is quite dark, so I'm not sure what you have coming out of the wall. Is that a 1-1/2" PVC Schedule 40 45 degree elbow at the wall, followed by a hub trap adapter, followed by a short section of white 1-1/4" tubular pipe, and then the grey tubular pipes?
Let me upload a brightened picture:
- The short section of white 1-1/4" pipe you're seeing actually adapts the white pipe which is 1-1/4" with the snappy trap, which is 1-1/2". this came with the kit, slid into the threaded end of the pipe, and was needed to attach the grey pipe to the white pipe. This is what I coated in pipe dope, since it was just a friction fit between those two white pipes.
- The grey tubular pipes then screwed onto it accordingly.
If that's right, then suppose you extended the white tubular pipe along its current path, and extended the sink tailpiece down. How much would they intersect or clear each other? I.e. 0" is just touching each other, or 1" clear means a 1" gap at their closest approach, , or a 1-1/4" intersection (the outside diameter of 1-1/4" tubular) would mean they line up perfectly and their centerlines would intersect.
Yes, you are hitting at the crux of it, I think. I don't have an exact measurement here, but if you extended the centerlines of those two pipes out, they are almost perfectly coincident--probably the lines are 0 to 1/4" apart, meaning the corresponding pipes interfere. When I was installing, this was the problem I had because both the short and long horizontal tubes (not pictured) that came with the kit as alternatives to the flex hose directly interfered with the sink downpipe extension needed to connect to and complete the U-bend.
If they clear each other by not too much, it should be possible to have your u-bend turned so that the white tubular (if extended) would pass right over the u-bend outlet. The u-bend would mostly point away from the white piping. Then the trap elbow would point back towards trap adapter and be in line with it.
This very correctly describes what I couldn't do because of the interference. I think to get something better, I'd need a rather compact connection and U-bend coming out of the white pipe, so there was room for the U-bend to fit the other way without the pipes crossing over.