I weighed the tanks on the scale this morning.
The 30lb tank of new freon attached to the charger weighed 7.5 lbs. I swirled it and there was indeed some freon left in there. In the brief research I did I found that they weigh about 5 lbs emtpy. So it appears I have ~2.5 lbs of R12 in that tank.
The 50lbs recovery tank weighed 43 lbs on the scale. I was flabergasted. I am having trouble believing that the dry weight of this tank is 5.9 lbs as shown in the Grainger link above since the tank is so much larger than the 30lbs new freon tank. I would guess it is closer to 15 perhaps more. But any way you slice it I have well over 20lbs of R12, maybe even closer to or over 30! That freon alone would cost WAY more than the $95 I payed. I think I'm set for a long time on my AC needs!
