the easist way is to drill the lock...dont drill all the thru though and get metal shavings inside the tank....after drilling it, you can take a flathead and use it like a key to unfasten the lock. just take your time and start with a small drill bit and step up a size. go thru about 3 or 4 different bits, each one size bigger than the last and that should get it. thats how i did mine