I have a 60 gallon PVC drum that I use for spare water at the races. I fill up the barrel then lay it on it's side in the bed of the truck. On the barrel cap I have a fitting with a hose connection and a valve. I am able to hook up a hose and gravity drain the barrel into my fresh water tank. I also use an electric submersible fountain pump that I purchased for about $15 at Harbor Freight. I bought about 20' of the clear plastic water tubing which hooks up to the pump and I run it into the fresh water tank. Pump transfers the water very quick and it works great.