I am sure this has been talked about before but there are so many pages lol. I am new to brewing and I had batch do a blow off. I added the blow of hose and put that into a small bucket with Starsan in it. My question is when the blow off is done is it best to go back to the airlock or leave it be?
Either way, doesn’t matter. If I’m moving the fermentor from one place to another (like out of a fridge or to a different room in my house) I’ll switch the blow off tube with a regular airlock. If I’m not going to move it for the duration (2-4 weeks), I just leave the blow off tube in.
To me it makes sense to switch back to an airlock, which I always do. I reason that following the end of blowoff, the empty tube with yeast residue, depending on how long left that way, could breed bacteria which airborn could work its way back into the beer. It’s very easy to swap out with a sanitized airlock, and also it’s easier to clean out the yeast in the tubing if it hasn’t had lots of time to harden in there.
If your blowoff tube is submerged in starsan solution, you shouldn’t get any bacteria growth. Like mrv said, a blowoff tube is essentially a big airlock. CO2 has pushed all the oxygen out and with the tube submerged in some sort of sanitizer, nothing bad should get back in. Having said that, switching over to a regular airlock is also fine. If you’re not moving the fermentor around, there really is no need though.