i had a customer do that to some cylinders on a 300 ton low boy trailer,
they were driving it without the pins engaged to hold the trailer part up
just riding on the oil in the 10 inch bore cylinders , a few bumps down the
road and shock poped the 10.250 x 12tpi glands right out of the tubes taking
the threads with them , wish i could have seen it , dropped the loaded
trailer on the highway at 45 mph!


but back to topic , weld it then fill it with water and pressurize it with
50 pounds more pressure than you will operate it at and yuou should be ok

or , go down to the local pawnshop and buy one with a blown up pump or motor
just for the tank