First, happy thanksgiving!
I have 2 gallons of cider down right now for the SWMBO. It is in a 5 gallon carboy in my new wine fridge/ferm chamber. With a five gallon carboy there is not enough room for an airlock, so I put a 2-port cap on the carboy and ran a piece of tubing to an airlock sitting elsewhere.
The cider is fermenting away, lots of bubble of the trub (got an inch of trub in 1 day!. When I open the door, I can smell the fermentation clearly, so I know gas is escaping, however, I cannot detect any movement in the airlock (twin-chamber style). The tube connections are tight, so could gas be escaping from under the carboy cap? Maybe with the length of tubing, it is easier for the gas to escape elsewhere? I used this cap before in a blow off rig for a DIPA and it worked fine, but it does feel a bit loose (it rotates easily around the mouth of the carboy).
There are no signs of infection, and the cap and the chamber should keep most stuff out, so I am not overly concerned, but I wanted some input.