No bubbling through airlock

Beginning homebrewer in San Jose here.
I have a 3 gallon FastFermenter that I am very happy with, but there is 1 thing I do not understand. I’ve been brewing 1 gallon kits from Brewmaster that I purchase at MoreBeer. I’ve lately been combining 2 of the same kit to yield a 2 gallon batch, which gives me 16-18 bottles. After chilling, I pour the wort into the FastFermenter, pitch the yeast, and wait. With this procedure, there is never any bubbling/activity at the airlock. I wait 2 weeks, then bottle the beer, then let it condition for another 3 weeks, then drink the beer. It is always good. I cannot measure the beginning and final specific gravity as my hydrometer tends to bottom out, so I don’t trust the reading, and just use 2 weeks and 3 weeks as my milestones.
When I brew just 1 gallon, using a 1 gallon glass carboy for fermentation, there is always lots of bubbling, and in fact sometimes a mess to clean up.
So, is there an explanation for the lack of bubbling at the airlock? The beer tastes fine. Might it have something to do with the “headspace” between the beer surface and the lid of the fermenter? A gentleman at MoreBeer said I must have an air leak in the system, but I can find no evidence of that.

I’m not familiar with the Fast Ferment. If your beer reaches the Final Gravity and tastes good you have a leak in the system. I use buckets as fermenters sometimes and if there are no bubbles I we work sealing the lid, and Schazam, i get bubbles in the air lock.

Yes, the CO2 is escaping before it gets to the airlock. I’m not too familiar with the fast fermenter, but it looks like it has a screw on lid. Make sure that it seals well.
By the way, didn’t your hydrometer come with a sample tube/jar? If not maybe you should get one.

Don’t rely on bubbling to confirm or rule out fermentation. Your only sure fire method of knowing is taking gravity readings. As others have suggested you must have a leak in that fermenter somewhere. Escaping gasses will take the path of least resistance and that often times means bypassing your airlock.

Waiting two weeks before bottling is normally ok, but there is always a chance you will have a slow fermentation. Many brewers who bottle condition wait a reasonable amount of time, then check gravity twice, three days apart, to be sure gravity is stable. If gravity has dropped, it’s not finished - wait and check again later. If you bottle before fermentation is finished, it will finish in the bottles - you could get bottle bombs (literally). Since you are brewing small batches, gravity samples might reduce your final output too much. You could use a refractometer and adjust the reading by using an on-line correction calculator.

+1 refractometer. Drops vs. ozs.

+1

Thanks everyone for your replies. I did not have a sample jar with my hydrometer. I just bought one along with a “thief” for pulling samples. I brewed a 2 gal. batch of wheat ale a few days ago, measured the gravity at 1.054 just before pitching the yeast. Still no bubbling. I cannot find a leak. Have screwed on the lid of the fermenter as tight as possible. Will measure the gravity again at about 7 days and depend on that as well as time passed as to guide my next steps.