Before re-finishing the fuel tanks we decided it would be wise to leak test them first. The best way to do this is to seal off all of the openings, fill the tank with some air under light pressure, and then dunk the tank in a large container filled with water. Any leaks will immediately show themselves as bubbles in the water.
With dad in town for a few days this was a job that was perfectly suited to his masterful skills of ingenuity. Needless to say he did not disappoint as he cleverly used an old bicycle inner tube to not only seal the tank, but he also took advantage of the air valve to give us a place to pressurize the tank from. Simple, effective, and cheap we had the tanks tested in no time and are happy to report that there were no bubbles so we have no troubles.