Finding fresh water.

It is much easier to just fill at home than to search for and find an unknown questionable public water source.

Flying Js almost always have fresh water at the RV fuel pumps.

Sometimes they will have trucks come around with water....you might be able to purchase it from them. They normally have pump trucks that come around to dump your tanks also.

Also, call the track and ask them this question. They deal with thousands and thousands of campers every year.

Check rest areas and truck stops on your way. I am not sure what would be the closest. Hickory Run State Park in not too far from the track.