That is something that has bugged me. I have a leak in my car's AC. I have injected the dye, found where the leak is. All I have left is to open the system and replace some old seals, but I can't do that right as the equipment isn't available. So I'm stuck venting to the air as it is the only thing I can do. (I could of course take it in, but some combination of cheap and doing my own maintenance means I don't)
Note that the vacuum pump is often a free rental from the auto parts store, I don't know why they can't/don't rent the recovery equipment.
Try taking it to an AC shop & pay for a 2-part deal: evacuate it now, then fill it back up in a few days.
When you put it back together you can pull a vacuum on it, close it off and make sure it stays that way overnight. But you may still want to have a professional shop test with higher precision than whatever gauges you use.
Seconded. I found a local mechanic and it cost very little to have them remove the existing refrigerant. They also kept track of the amount removed (which ended up being very little) and offered to put it back in after the leak was fixed.
Note that the vacuum pump is often a free rental from the auto parts store, I don't know why they can't/don't rent the recovery equipment.