I live out in the Southern California desert and often thought to make an emergency water tank, but how? I know you can buy plastic tanks, but they are expensive to ship. I've seen metal round ones, but are there plans to make your own? Do I need a platform? How tall off the ground should it be? How to keep dirt out? How much water to hold for a family of 4 lets say for a week for drinking and cleaning? Do I need a pump too? I know thousands of people rely on water tanks so other then buying a fancy plastic tank, surely someone has directions on how to make it myself.