This is my "water transfer system" for boondocking. The pump came from a Harbor Freight store and cost about $20 bucks. I could have used a regular "surflo" pump if I had one but they cost at least $50 bucks for reconditioned units.
This pump uses 12volt power and is perfect for my use. To make it work I ran a long positive lead all the way from my battery to the back of my trailer and installed an outdoor 12volt receptacle. I put a male plug on the pump leads to fit the receptacle and installed an on and off switch in the positive side. The ground side went to a handy screw in the frame of the trailer.
Now I just back my truck up to the pump and connect a primed hose from the water bag to the pump. Flip the switch and in about 10 minutes my rig is full of water and I'm ready for a refeshement!
The mount under the pump is a scrap piece of 2x4, with a hole in the bottom that allows the pipe from a television tripod to be inserted rather snugly. I just set my TV tripod next to the trailer and the pump on top. It's the perfect height. The pump will work while positioned on the ground though so you don't really need it. I just like to have things at a handy height if possible.
I'll show you the water bag connection in another blog.