WHY would you ever want a site with just water? Makes absolutely no sense! An RV usually always has a freswater tank and you decide what quality of water from where YOU will allow in it. However, I've yet to see an RV with an electric supply storage tank to draw AC current from! Although it may have a generator or an inverter and a battery bank for some AC usages!
All a water hookup does without having a sewer hookup is quickly fill the holding tanks. So much more water is used for various needs when hooked up to an supply source in a CG than when it's pumped from a tank. Consult your holding tanks as they know so well.
Excellent quality water and all you want is what comes out of spigots in our state thanks to the huge Great Lakes but that's not the case in many states or CG's. We can hardly stand the putrid taste of the water in so many states and that's why they sell so much bottled water. Nestle Products Ice Mountain etc has a huge water bottling plant about 75 miles north of our home that bottles billions of gallons every year and ships all over. We even found the plant number on bottles of water on grocery stores in Florida and the other southern states. Good water is something we don't have to worry about in our state.