It is fresh water! Dump wherever you want to...
:?
Draining at CG site:
I have pulled into a campsite where the previous camper thought it was OK to drain his fresh water tank before leaving. How INCONSIDERATE. It makes the CG site all wet and muddy for the next camper. :R
Draining and driving down the road:
I don't want your water all over my car and when it's coming from an RV the person behind has NO idea if its fresh water or not. So the person behind IS gong to call it in to law enforcement.
So you will most likely get stopped by a cop to find out and good luck convincing him its fresh water which as far as he is concerned it probably won't make any difference and you will get a ticket for dumping water on the highway.
Drain your fresh water tank at home on the lawn. If you store your RV all the storage most have storm water run off drains. Pull over the drain and then drain your fresh water. But then again many states have laws prohibiting that too. So You'd have to check first.