Am not a plumber, but would assume that the pressure relief valve on the HW tank would be set by the designers to accommodate any increased pressure put on the system by increased temp of water in the tank. As Jagiven previously said, I have never checked the pressure on the system, nor do I have a pressure gauge. Never had a problem with the plumbing on any of my TTs or the current 5er. But I do have a pressure regulator on the water supply at CGs, which I believe limits it to around 50lbs.
2003 Ford F-350 V-10 Crew Cab 4WD Long Bed
2004 Jayco Designer Medallion 29 RLTS 5th wheel
Bill, Gayle, and Mindi (dachshund)
Retired at last !
Nothing is foolproof to a sufficiently talented fool.