Let me put it this way....
Most RV's have a sticker, it says "Maxium pressure" on it and then a number, usuallyu 40-50 PSI (This is near the city water inlet)
IN fact, Most everything in the RV can withstand 55-60 PSI, Id not wish to go over 55 though just to be safe.
One park I stay at they warn you right on the park map that they have MEASURED 120 PSI, and I have personally verified over 100PSI.
Do you need a regulator... Or swim trunks.. YES.
(Swim Trunks, why swim trunks... So you can swim in your brand new indoor swimming pool when the seals blow in the assorted valves).