A blow off assembly is a length of tubing which is attached to your primary fermentor to allow excess yeast and foam (krausen) to escape. During an especially active fermentation, the krausen can fill the entire head space of a carboy. Without a place for this foam to go, it can create quite a mess. An airlock can become clogged, but a blow off assembly allows krausen to be expelled from the fermentor while still making sure that nothing gets in. One end of the blow off is inserted into the fermentor, and the other end is submerged in sanitizer in an open jug or bucket. Keeping the end of the blow off tube below the surface of the sanitizer will keep a positive seal in the fermentor. There are several different types of blow off tubing assemblies depending on the type of fermentor.
A 1" ID blow off hose fits glass carboys. 1.25" Blow-off hose for older style Acid Carboys.
A length of ⅜” siphon tubing can be inserted into a bucket lid by removing the airlock and grommet if needed as well.