No need to flush the tanks, they'll empty as you go.
Open all the faucets (hot and cold) but keep the hot water tank bypassed and open the outside valves for your tanks.(black & gray) Flush water through the city connection until all faucets run clear. This can be done at the CG on your first trip. Once this is done, you can un-bypass the HW heater.
2013 Jayco Eagle 328 RLTS
2012 Ford F250 6.2L 4x4 CCSB W/Air Lift air bags
2002 Coleman Bayside Elite (traded)
Me, Momma and Charles (RIP buddy)
And introducing Sofie!! ;)