Years ago I too considered a large potable water tank but the question was - where to store it when not being used, especially during the off season? That convinced me to stick with inexpensive, easy to store 7 gal Aquatainers which live in the back of my truck when camping and sit on a shelf in my garage when we're not. I too use a SHURflo potable water pump for transferring water from the 'Tainers to the trailer's fresh water holding tank and with my current trailer have plumbed the pump output directly to the tank. The pump sits in a modified G24 battery box mounted on the tongue so to transfer water all I do is drop the input hose draw tube into a 'Tainer of water and turn the pump on ... couldn't be easier and with the trailer's tank being 30 gals using four 7 gal Aquatainers for collecting the water has proven to be plenty. :B