Thanks to all for the good (and quick) responses.
For the expansion pressure tank, I'm a little foggy on how installing that on the cold water side prior to the water heater will change anything. What am I missing?
Regarding temperature and pressure in the line--I didn't put a thermometer on it, but it gets wicked hot. Don't know how to measure actual pressure on the hot water lines, but they are very firm as opposed to the cold water lines. When I turn off the water pressure pump and open the faucets they become relaxed. I opened the pressure relief valve...water drained out as expected and the hose pressurized again once I closed it.
I have wondered about the type of hose, the main plumbing
in the boat
uses that solid plastic piping like they put in modern homes however for mating to pumps, faucets, etc the pipe is transitioned to that clear tubing with the braiding. Could it simply be this? And if so, what is the correct type of hose?