This is good to know. When I press down on the lid to the FV to in effect force some gas out of the air lock no bubbles appear either. The water just gets pushed out
My guess is your lid is leaking, but don't worry it will be sealed enough. The water will overflow out of the top of the airlock if it's too full, even with the cap on. I put it on just to stop dust, but again don't get too worried about it.
maybe there is a little too much water in the airlock but as the co2 builds in the F.V. it will push the water out and find its own level. I have started putting the lids back on my airlocks as the bubbling is less noisey with it on. I keep my F.V.'s in the spare room next to my bedroom and I thought the noise was the wife snoring !!! :rofl:
i like to fill my airlocks up to half way up the first bulb on each side, i've found that gives off the least amount of sound and it wont take to much pressure to shift it so you'll get nice quiet single bubbles.