my pressure tank has sprung a leak and is rusting out. I have a band-aid on it and will need to replace it very soon. I am having trouble finding draw-down numbers for the tanks I see online, and I don't know what kind of tank to buy. I currently have an old 80 gal. steel tank. I saw equivalent ratings for smaller tanks, but I also heard this was B.S. I have a in pipe and an out pipe on my tank, but the pre-charged tanks only have one hole? The tank is outside of a 3/2 house with a sprinkler system for a normal back/front yard, aprox. 40 ft well that has not run dry, yet. Anyone want to school a newbie?