More detail for my last post -- for EM, seal the fermenter with the SG between 1.020 and 1.010. Press the lid down firmly all around, and ensure the grommet or drilled stopper and airlock are firmly seated.I have a 7.9 gal bucket with gasketed lid that I purchased from label peelers. It seems to seal good. Any idea if they seal well enough for extended EM? Now I'm second guessing myself.
Shake the fermenter -- the airlock should bubble, as the active ferment expels CO2. If it's not bubbling, then worry that it's not sealed. As I stated above, air will take the path of least resistance, so if there's a leak, that's where the air will escape, not the airlock.