Maybe this has been covered but I thought I would share my recent experience.
Running water out of the kitchen faucet to flush out the pink I noticed water dripping out of the trim line outside. Of course panic ensues and like on my boat "where the hell is that water coming from" thoughts run through my head.
Pulled the drawers out of the kitchen and see that the black abs pipe is leaking pretty good.
If you blow up the attached photo and zoom in on where the 1 1/4 horizontal pipe meets the vertical 1 1/2 pipe you can see that fitting itself cracked. Oddly this is also in the same spot the pipe is supported by the clamp. To me it seems there is stress in that joint due to the alignment of the two pipes.
Anyway I replaced all of it and because it's really hard to find 1 1/4 abs pipe or fittings locally I had to improvise a bit.
Moral of the story is they used abs because it's supposed to be more flexible . There has to be alternatives that would prevent this from happening.
Just passing on my experience as the coach seems destined to drown itself and disintegrate the bulkhead.
You will find that ABS pipe is almost non existent now and replacing with PVC is fine, as long as you use the correct glue, which is all purpose. It will state that on the can. The PEX line could be the issue, as it is rather stiff and solving that issue would be to install SS flex line in place of where it makes those connection joints. I never heard of ABS being more flexible! Hope that helps!
So, of course, I immediately had to ask Google the "ABS or PVC" question. Learned some new (to me) interesting things about both materials. This is one of the reasons I really like this Forum. Almost every time I log on, I see a post that leads me to "further investigation", and ultimately results in my limited capacity brain being clogged up with more random information. Cheers!
PVC is just fine for cold water, but softens up with hot water. That's why drain lines are ABS. Spaghetti water.