water pump

You can fill the HWH with city water or from the potable tank.  Either way, open the hot water valve at the sink a little bit at let the air come out until it stops spitting and there is nothing but water coming out of the tap.  If you're filling from the potable tank you might want to top it off.  Then you're you're set to turn on the gas or electric element.

TT 

Originally posted by GLBCamper Is the hot water heater filled simple by connecting to city water, or do I need to do something else? How can I tell if it's full before turning it on, so I don't burn it out?

Originally posted by GLBCamper Is the hot water heater filled simple by connecting to city water, or do I need to do something else? How can I tell if it's full before turning it on, so I don't burn it out?

You need to bleed the air out of the water heater. Open your hot water faucet let it run till it stops sputtering and a little extra just to be sure. This is especially important if you use the electric heater. If the heating element is not fully immersed in water it will burn out in very short order.

Another reason to do fill you water heater at home.  If you do this on the road and you are dry camping you may be using up valuable gray water capacity. (IF that is a concern)

Is the hot water heater filled simple by connecting to city water, or do I need to do something else? How can I tell if it's full before turning it on, so I don't burn it out?

If you don't mind carrying water, fill the tanks at home.  Get everything working right in the driveway then shut it off for the trip.  should work again.