Well,
I carry a small, 1.3gpm Karcher Pressure washer. It's smaller than the EU2000 Honda Generator. I set up a water supply for it from the water pump. I also have one of those fold-up ladders. It takes me about 1-2 minutes to get setup for a wash job. Yep, I've encountered many camp grounds/RV parks that frown on you washing your coach.
But, they do allow for a "private" company to come in and wash it for you, AT A SUBSTANTIAL COST! So, if ours is getting bad, I find a remote corner of a Kmart or, Walmart or, Home Depot or, any other large parking lot and, park in the corner and go at it with my little setup.
I've even done it at larger rest stops, in a section that I'm not in the way. I can power the pressure washer from either the Inverter or, the generator, depends on my mood at the time.
Now, this is one of those things again that's COMMON SENSE. I don't have gallons and gallons of water running all over the parking lots etc. As I stated, it's a 1.3GPM Pressure washer. You can just get it wet enough to soap and brush down, then, just barely enough water to do an efficient rinse. The whole process, start to finish, setup, wash-rinse, dry and put things away, takes us about an hour.
We use our own water, and, there's no mess. The rinse water barely puddles at the base of the coach. This system works real slick.
Scott