I had a similar question on my '13 25RKS and since I have been full-timing in it this winter I decided to add heat tape and insulation to that long run of exposed pipe. Not sure what the factory could have done but it seems like leaving that long run exposed is a risk in freezing temps. If you are using your trailer in the winter I believe that you should at least add insulation.
2013 Jayflight 25RKS - Picked it up 4/13/13
1999 F350 7.3 Crew Cab Long Bed Dually
1995 Dodge B3500 (Semi-Retired Now - nearly 400K miles)
On the edge between Far West TX & Eastern NM