Adding additional water tank to TT

Camping for long periods in the Arizona desert, we frequently need to add additional water to our tank. Our current FW has the ability to pull water from an external tank. But in the past, we'd carry water jugs in the back of the PU. When we needed to add water, we would use a hose and a portable 12V pump that would allow us to pump water from the jug to the main water tank without having to lift the full jugs out of the truck. The nice thing about this set up was that once the jugs were empty, we could refill them anywhere there was water available without having to move the trailer.