Whoops! I re-read your post and see you were referring to the FRESH water tank not the "holding tanks." My mistake as the holding tanks are terms usually saved for the gray and black tanks.
Since there are check valves in the feed system, you don't have to do anything different except make sure the pump switch is "OFF" when hooked up to city water.
There is a check valve in the inlet to the pump (from the fresh water tank) that keeps city water from spinning the pump backwards and filling your fresh water tank.
There is a check valve in the water hose connector (outside) that prevents water from blowing out the side of the camper when you are pressurizing the system with water from the pump.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW