water line problem

A pressure regulator (what wolfe10 calls a pressure reducer) is sometimes needed, as some camp "city water" supplies are at pressures too high for RV plumbing. I don't know about your rig, but the owner's manual for mine recommended one and specified that the plumbing was only to be pressurized to 60 PSI. I was at a campground once where the city from which they got their water insisted on supplying it at 150 PSI. If you hooked up to that guy's water system without one, I'd anticipate something like the water pump cracking and leaking, if not somewhere else simply blowing out.

Water pressure regulator is like an electric surge suppressor: you might get away without it for years. You also might have bad things happen the first time out.