I believe Dutchmen/Keystone is still using Pex Pipe for the water lines.
Your stock water pump is rated at 40 PSI
The Pex Pipe max would be around:
"Uponor PEX carries the following hydrostatic temperature and pressure ratings: 200°F at 80 psi. 180°F at 100 psi. 120°F at 130 psi (1/2" Wirsbo AQUAPEX tubing only)"
I personally would not exceed 50 PSI, the plumbing routes in these things would be a pain in the rear to trace for leaks and/or replace broken pipes.
2015 GMC Denali 3500 DRW
2014 Dutchmen Voltage 3950
Toys: 2010 ArcticCat ThunderCat 1000, 2012 Yahama Raptor 250, 2012 Yahama Grizzly 550 EPS, Canoe, Kayak