Foe me I use a 35gal drum to hold the water as I pass through a town or other water source. I than use a 1/2"pvc pipe the has a slight angle cut on the end that goes to the bottome of the drum and out the top I attached a 90*elbow with a threaded hose end to it. I than hook up one lengthy of hose to the pvc hose fitting and the other end to a 12vot pump that I bought off Amazon (seen similar pumps at hf) and the has clips that attach to the battery. I attach another hose to the outlet of the pump and to the rv and connect the pump to the battery. It amazed me how fast it drained all the water the first time. I always leave the drum straped in the back of the truck when I'm out there.
I still use a 8gal container that I modified with a hose attachment and just gravity feed as well. It just depends on what type of trip we are on.
