I'm working with a new shielding gas regulator, and when I first fitted it to the cylinder I there was a leak at the nut where it connects to the cylinder. I tightened the nut and then pressurized the regulator only: flow valve off, cylinder valve open to show 2000 psi on the contents gauge, then cylinder valve off.
Then I left the room to get a cup of soapy water for additional leak testing. During the 2 minutes I was away the contents gauge lost about 400 psi, indicating a leak somewhere. I tested all the fittings on the regulator and found the connecting nut was still leaking, so I cranked down on the nut, applying more torque than I felt should have been necessary. This stopped most of the leak, but bubbles still form under pressure.
This is a very minor leak but my question is: what amount of leakage is acceptable? It's inert shielding gas, not going to flash, in the garage so not in a living space. Is the acceptable level zero leakage?