There are other posts on this as well. here is what I do.
Hook up the city water and flush the crap out of everything through the faucets etc all on at the same time. Turn off the water supply, Then close all the faucets, open a low drain if applicable and drain everything. Pull anode rod plug rinse out inside hot water tank. Reinsert plug only. You can sanitize the lines with a mild bleach solution, then redo the whole flush again only replace the anode rod this time. close all drain points and you should be good to go. OR, just hook up to the city supply and flush everything out by running water for about 30 min and leaving all faucets on but open grey and black tanks to flush all the crap out. The new antifreeze is supposed to be non toxic, but at one time they told us not to drink milk or eat butter. As for me, I will sanitize the lines, not that having a third eyeball growing out of my neck would be a bad thing....
have fun and Happy Camping!