Blow-off tubes - When to use?

What are the guidelines when using a blow-off tube instead of a more traditional (I use 3 piece) airlock?

Is this for the more krausen-producing yeasts like belgian strains? Or maybe is it for when your pitch rate is really high?

Thanks.

I always use one for at least the first 3-4 days. You never know when she will blow! Especially with a new yeast strain or recipe. It is alot easier that cleaning up yeast goo from the bottom of the ferm chamber.

Up until now I have been using 5 gal buckets for 5 gal brews and it doesn't leave much headroom. 1/2 gallon to be exact. I had to have a blow off for the first 2/3 days at least. I just got a 6.5 gal bucket and now the air lock is fine.

I use a 6.5 gallon carboy and don't have any issues. Until you have brewed different styles with different yeasts you should always use one until the krausen peaks just to be safe. After that, you'll know whether or not you are going to need one based on what you are brewing.

Depends on what i'm making and how much. If you have a gallon of headspace or so, you are typically okay. I prefer to leave 2 gallons if possible. Split a 10 gallon batch into 3 carboys... But if I do a 6 gallon batch, 5.5 into the 6 gallon carboy, a blow off is a must! I switch them out after a few days and clean them asap. I've switched them out after 3 days and then had blow off before, too so be careful!

Almost never. I'm with the over sized fermenter crowd. Why let yeast walk out the door without doing its job?

You can never predict how the fermentation is going to go, so I always use a blow-off on my 6.5 gal. primary carboy. Better safe than sorry. If I do a secondary (for dry hopping or extended fermentation), I use a 3-piece airlock on my 5 gal. carboy.