5 liter jug headspace

[a_zavala]

Hello,
I'm new to HBT, this is my first post. I've read some threads about blow-off tubes, and 1 gallon jugs, but I'm looking for a pretty straight answer to this question and couldn't find one.

I'm about to start doing 1 gallon batches at home. I bought a 5 liter jug, I attach a photo

I was wondering how much volume can my batches be. Clearly not 5 liters, that's almost the full jug and I guess it'd make a mess even with a blow-off tube, or I could lose a big portion of the batch, right?
So, what's the most I could ferment in this jug? 4 liters? would 4,5 liters be too much?
And would a blow-off made with a rubber bung, part of an airlock and a 3/8”-1/2” tubing be ok?

cheers!

 

[RM-MN]

The reason you didn't find a straight answer is that there isn't one. Yeast do their own thing and we have no control over them. One batch you brew might be fine at 4.5 liters, the next might spill over with 3.5. Much will depend on how much yeast you put in there and temperature of fermentation will have an impact too.

Personally, I'd probably set that jug into a tub that can contain any spills and cover the jug's opening with a cling plastic film that has a pinhole in it. The pinhole will let out the CO2 and if the jug spills over the plastic wrap will come lose so it doesn't spray all over.

Once the fermentation slows down you can wipe off any spills and insert a plug with airlock.

 

[ESBrewer]

I have two 5 liter carboys and I use some 4 liters of wort in fermentation. There was no problem with the first batch. At the moment the krausen almost reaches to the top of the carboy. That's not really a problem as I have a sanitized blow-off tube that leads to a 10 liter bucket with some Starsan in it...highly recommended. Just cut the tail end from an airlock and take some snug fitting pvc tube (not the one with very thin walls - it bends too easily and may get clogged). You may need to heat up the tube in hot water to get it in place. Put some weight to the end of the tube so it stays in the bucket that contains sanitizer.

 

[a_zavala]

The reason you didn't find a straight answer is that there isn't one. Yeast do their own thing and we have no control over them. One batch you brew might be fine at 4.5 liters, the next might spill over with 3.5. Much will depend on how much yeast you put in there and temperature of fermentation will have an impact too.

Personally, I'd probably set that jug into a tub that can contain any spills and cover the jug's opening with a cling plastic film that has a pinhole in it. The pinhole will let out the CO2 and if the jug spills over the plastic wrap will come lose so it doesn't spray all over.

Once the fermentation slows down you can wipe off any spills and insert a plug with airlock.

thanks for the answer! I'd never heard about using plastic film at first, that's interesting. But I live in a tiny apartment and I don't think I can fit a tub with a messy fermentor in it for a few days and get away with it. I think I need to keep things cleaner. I can expect a blow-off tube leading to a bucket to keep the place cleaner, right?

 

[a_zavala]

I have two 5 liter carboys and I use some 4 liters of wort in fermentation. There was no problem with the first batch. At the moment the krausen almost reaches to the top of the carboy. That's not really a problem as I have a sanitized blow-off tube that leads to a 10 liter bucket with some Starsan in it...highly recommended. Just cut the tail end from an airlock and take some snug fitting pvc tube (not the one with very thin walls - it bends too easily and may get clogged). You may need to heat up the tube in hot water to get it in place. Put some weight to the end of the tube so it stays in the bucket that contains sanitizer.

Thanks for the advice, I guess that's what I'll try first then, about 4 liters, and a blow-off tube fit to the bottom part of an airlock.