Main water line blew off, flooded underbelly

[tigerGUY1955]

That strand board is destined to be replaced once she's wet for any length of time. Replace with 3/4" marine plywood and spray both sides with bed liner material. You're welcome.

[huntindog]

Drop the coroplast, pull the insulation and toss it, as it will take weeks for it to dry. Let things dry for 2-3 days then put new insulation in (or not) and reinstall the coroplast. This takes a helper but it’s not hard.
The unfaced insulation like the factory used will be hard to find, but you can peel the craft paper off some R-13 and use that.

Last comment re regulators. I’ve seen more RV regulators that don’t work than those that do. Most of them will leak internally allowing full line pressure to hit the plumbing. You can see this as a short burst of high pressure when you first open a valve, then it drops off..if you see this your PR is doing nothing for you.

I would not reinstall that type of insulation When it was originally installed, it was just a frame that was upside down. So the installers had gravity to help them. You will NEVER get that insulation installed like it was. And worse, when trying, you will be showered with tiny particles of it.... DO NOT breath that in. I used a PM 100 filter with a full face shield to keep it out of my eyes and lungs when I removed mine. I replaced it with rigid polyisocronate insualtion board custom cut to fit. I also replaced the coroplast in small sections, to make future access much easier. The rigid insulation has A R6.5 rating per inch. I put as much in as would fit.
Yes it was a time consuming project, but it really made a big difference insulation wise, and future maintainence will be easier, so there IS a payoff for the upfront work.