So, I wanted to test my fuel tanks before mounting them to the fuselage since it’s been only since 1999 since they were built. As the photos show, I set up each wing on sawhorses, grounded the wing, plugged the fuel tank outlet and quick drain, and added 10 gallons of avgas to the tank. I spread copier paper out under the tanks to catch any leaks and hopefully show blue stains if there were leaks.

Bottom line is that no leaks were detected after leaving the tanks unattended for more than 24 hours. I then pumped the avgas back into gas cans using a small Facet fuel pump and filter. Nothing was caught in the filter. As far as I can tell, the tanks are ready for mounting on the fuselage.