Originally Posted by Glenn Baglo
If you connect to city water and then open the relief valve ( pix ) and let water flow for a few minutes, you will ensure that the tank is full.
Glenn's suggestion is the best way of making sure the tank is full of water and not half full of air! I know on a couple of occasions I thought the hot water tank was full but it was not - had to much air in it. That commonly happens the first time you refill the hot water tank if it was recently completely drained from the outside.
The other thing to keep in mind is that the hot water tank when dry camping
will pull water from the fresh water tank to refill itself as the hot water is used. When filling your fresh water tank for a camping trip, you want to make sure you have actually filled the hot water tank as well. So make sure you turn on the water pump so that it also fills the hot water tank. If you do not do that the first time you turn on the water pump it will use up a large chuck of your fresh water tank supply to fill the hot water tank.
Adding bypass controls to the hot water tank is also a good idea. That way you can stop it from pulling from the fresh water tank if your water supply is running low.