If you connect to the campground water, it should fill the hot water tank as it pressurizes the system. Ist time out you may have to open faucets to let air out of the system.
But- If you have no hot water from the hot water faucet, the water heater may be bypassed (winterized) your manual should show how to set the valves at the water heater back to normal use. Operating the water heater with no water can damage the tank....
FWIW I put a red tag on the water pump and heater switches when the tank is bypassed and I winterize.
__________________
|