I sanitize my rv with 1/4 cup bleach per 15 gallons in the tank fill the lines then let it sit over night. Drain refill and flush. However we never drink from it. I have yet to see backflow preventers in cg's so you really dont know what germs are coming from some dude 12 sites over. An example was the guy next to us last year. He parked set up then also connected his black tank flush to water line on the mast. Disgusting.
I dont know about you but im not going to drink his S**t. We always bring bottled and I use a large whole house filter that I install in line from the cg to the rig.
Happy trials