When I was welding my new mid mount stabilizers on Wednesday I noticed the same thing. Two white tubes, (pex) hanging between the axles. I assumed they were some type of over flow. I didn't even know I had two fresh water tanks until last week.
2015 338RETS Eagle Premier gloss sides., king.
2012 Ram 3500, crew cab 4x4 duelly Deleted
16k miles, 530HP, 1000 +torque.