if it's your first trip I would fill at home and watch for any gas stations or truck stops that would let you fill with water. I don't know about other states but here in Oregon for public use the water needs to be tested annually. the places we like to go boon docking have places along the route that we have used many times. One gas station we hit before the mountains, the old guy told me we are most welcome to use his water spout to fill any time we are there. the town ship also has dump station and fresh water spouts for travelers.