Originally Posted by ill4delph
I have the 7.9 and i honestly don't think that you will EVER need a blowoff tube, or have to be worried about too much krausen in that thing, if you brew 5 gallon batches.
I use that one as well, and it is awesome. It has almost 9 gallons of internal volume. I've done a couple of 5-5.5 gallon batches with the 1469-West Yorkshire yeast recently which is notorious for massive krausens, and I've had no blow-off. The latest, which is just finishing up, had probably 3 gallons of krausen on it, but nothing came out.
The awesome thing about the bubbler is that it is so huge that you can sit and count the bubbling rate out of the fermenter. Over my last two brews, I've followed the bubbling rate as a function of time, and it's made it really easy to see how the fermentation has progressed, and determine when it was done.