We use city water when available if of reasonable quality but still with a good filter to get any chlorine or nasties.
Sometimes we fill tand and use from it, if the water pressure is low during part of the day.
We have encountered parks where water pressure was 80 lbs or more. Get a good shower then. I have as we all have accounts of lines bursting or fittings coming apart with high pressures. we have a pressure regulator..which we sometimes use.
We generally get a better shower off our tank with 55psi pressure than most parks service which seem to keep pressures in the 30-40 lb range which is too low.
As to water fill check valve blowing out, we have read accounts here and I think seen it once. It could burst the tank perhaps. I accidentally filled too long and had water coming out of the fill port on the side of the coach.
One thing that will insure the integrity of the fill check valve is to always filter the water before it gets to it.
It is perhaps a great idea to turn the spigot off at the post when leaving, and certainly not imprudent to just fill the tank and use from it.
But...is life that uncertain?