my best advice to you would be to not use that tank anymore! In my experience, when these things fail, its typically catastrophic, and it usually happens when they are being filled....which could mean hundreds of gallons of oil on your cellar floor, or worse yet, on your DIRT cellar floor! The reportable spill quantity of fuel oil is 10 gallons, above which, first responders are REQUIRED to report to the DEP......and the DEP doesn't care who cleans it up, but they want it cleaned up, and immediately! Can easily break most folks financially. You can wait for the insurance company, if you're covered, but an old tank like that....who knows.....insurance co's have lots of lawyers, on staff.