Fresh water tank. This baby is an air pressure tank. We are debating taking it out and replacing it with a plastic tank with an electric pump. But, do we really want to change it out? What are the advantages? How long would a pressure tank hold pressure? Is this set up for wilderness camping as not to have electric? How many pounds of pressure is advised for these tanks? Is that enough to empty the tank or do you have to air up again before you run out of water?