As speedbump has stated, (and I agree), Most Vertical Galvanized tanks Rust out in the bottom 6, to 12 inches!. Now since the price of a new tank,(300 plus gallon), can cost many many Dollars. Has anyone ever cut, and removed the rusted bottom portion of a tank, and weldled on a new botttom cap?. I know you have to have the proper tools, ie., a cut off grinder,and or cutting torch, and welder,(and know how to use them),(which I do), But I wonder if it is cost effectivive to do this? The other thing that would have to be done, is drill, and install new weld-o-let taps for your supply, and outlet Taps! I know that where I live, a new 315 gallon tank cost close to 2 grand. Call me cheap, But if you have the will, Why Not? I have priced out the weld-o-lets (25 or so bucks), but not a bottom cap! My point is Money is Tight, and why not, If it does not cost more than the Trouble, and Cost of a New Tank!