Grey water pipes snake around above floor - can I reroute?

[Theophania_Rex]

I'm looking to convert the back bedroom of my 1995 Leprechaun into an open studio space. However, what appears to be the grey water pipes snake from the shower and the sink on the opposite side, run along the walls, then snake back under the bed (in the picture the pipes are under the long carpeted blocks) before going under the floor at the foot of the bed.

Right now my idea is to raise the floor in the room a few inches to accommodate so that I can have a mostly flat, useable area (I can cut down the blocks in the middle of the room a little, can't do it with the ones along the wall because of valves and electrical lines and stuff), but I'm also wondering why they are installed above the floor anyway, and why the heck they needed to snake them all over the place instead of using more direct lines to the dump valve. Would it be possible to just rerun the pipes to have them go under the floor in a more direct manner, do you see any issue with this?

Raising the floor poses issues of tripping over the step as I walk in as well as decreased headroom.

Thanks!

[BarneyS]

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Barney

[DrewE]

There's doubtless some reasons for this. The two possibilities that come to my mind immediately are keeping the pipe running downhill and not having to cut into/through the frame supporting the motorhome under the floor.

If there's room to run it under the floor, and you can maintain proper slope, the only possible difficulty I can think of offhand is that you'd be more likely to have the pipe ice up in freezing weather. I don't think that would be a big problem in practice since it shouldn't generally be holding still water, and you aren't likely to have it freeze in the short time it's between the sink or shower and the holding tank. I suspect, though, that it won't be possible to maintain sufficient slope without compromising the structure of the motorhome (and possibly even if that is done).