It's worth reminding folks that we are talking very low pressure here, in the order of one PSI or less, if you don't want to blow up your tank. I've checked my lungs with a high resolution pressure gauge, and I can bearly blow 1 psi, for an instant. The balloon method prevents disasters that can happen when using an air compressor for this job. Personally, I build the bottom of the tank and fill it with gasoline for the night, and come back and check it the next day, then install the top onto a bed of flox, and glass the outside of the joint again. By filling the bottom, you at least prove the critical bottom four joints are good before you button the whole thing up. If it leaks around the top, you can either fix it or don't fill it quite all the way up. N56ML's header tank was that way, but I learned from the experience and never had another leak on the other two tanks.
Mark Langford ML at N56ML.com http://www.n56ml.com
