I was looking for a leak on a rooftop condenser and the leak was in what appeared to be a hairline crack in the elbow next to the compressor. I brazed the crack and filled the system with the nitrogen left in the bottle to about 20 lbs. then proceeded to pull a vacuum and the low side pulled down to about -15 lbs PSIG. I obviously should have been better prepared but I figured all was well so I charged the system with R22 and the elbow split on a completely different spot than the original leak. I proceeded to close the king valves and by the grace of god I lost hardly any refrigerant. Anyway, has anyone else experienced any factory defective copper fittings or could it have been something else?