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Bribie G

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No, the title of this thread didn't accidentally miss out "babes" or anything so settle down chaps.

With my SS Brewbucket I'd been using an old fashioned two piece airlock, but since San Diego Super Yeast came back I've been doing the following "blowoff" arrangement, as a precaution (not needed as it happens);

blowoff.jpg

As you can see, a 1.25L springwater bottle half full - with springwater as it happens, just drain of half for kitchen use then pop the hose in.

This works fine, perfect seal on the lid and bung so it's a good method of monitoring progress as I can't see into the FV and fairly kitten proof.

Now after the bloops subside to one every half minute or so I've been reducing to near zero for a week then transferring into a CO2 filled keg. Last three brews the blowoff bottle has been empty on keg transfer.
First two times I thought "strange".
Yesterday the penny dropped, as it should have done, and I thought "****, Bribie, how could you have missed that one".

Clearly on cooling, the volume of the beer has decreased and also the volume of the gas in the headspace - I mean the volume occupied by the molecules of the gas - and there has been "suck back" - to the tune of about half a litre per brew in this case.

No deleterious effects on the beers that I noticed - there has been some slight dilution of course but I've escaped infections as the system has been pretty sterile to begin with. I'm just concerned that after the suck back of the water, then some air would probably been sucked in as well. Nasty 02.

Solutions?

1. Removing the bottle prior to cold conditioning in the Brewbucket would result in the same amount of air being sucked back in. Not good as I'm on a reduced oxygen regime.

2. Transferring to intermediate cold conditioning keg in a non-02 environment would work but double handling and loss of beer.

3. Collecting CO2 into bag towards the end of fermenting and letting this get sucked back into headspace of FV.

I tend to go with #3 and looking at attaching a bag (e.g just large common freezer type bag) tightly taped to end of hose. Fermentation slows to a crawl, bag slowly inflates, then deflates as gas later sucked back in. We only need about a litre capacity I'd guess.

Fermenting under pressure in a closed system? Yup got all that already, with a modified cornie and a spunding valve, just talking about using a Brewbucket. And of course this situation would arise with most other FV types used to cold condition in FV including cling wrap.

Anyone done anything similar?
 

TidalPete

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I’ve found that a larger diameter blow-off tube (combined with a half-full 3-litre juice container of boiled water) works well. especially when using top-cropping yeasts where you want to save the (blown-out) yeast but that’s a subject for another thread.
Just a two birds\one stone sort of thing.

Upon fermenter volume shrinking due to the cooler temps, the larger volume of air in a (bigger diameter) blow-off tube is much more resistant to suck-back than a smaller diameter tube used in conjunction with a normal ½” airlock.

Of course, with the BB only holding 26 litres against say, an ss olive oil brum of 32+ litres, it stands to reason that a bigger diameter blow-off tube is more advantageous in that situation.

My 2-cents.
 

Moog

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i always use starsan in my airlock, when I re-set for cold crash, I empty the airlock, and replace with a wad of cotton wool, a tip I read off the net, the cotton wool is sterile, and acts as a filter to clean the air going in, works good, not had any infections, although neither did I when I used to get starsan sucked back in.
 
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mtb

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A non-return valve in that blowoff tube? You'd end up with a vaccuum in your Brewbucket though..
ed: How about this - non return valve inline on your blowoff tube. At the end of the blowoff tube, a gas disconnect. During fermentation the blowoff disconnect is connected to a carbonation cap and flows into the springwater bottle as normal, not sealed.
When you start the cold crash, disconnect the gas DC. Vaccuum forms in the Brewbucket and the blowoff tube.
On kegging day, connect the gas disconnect to your CO2 filled keg to allow CO2 to flow in and negate the vaccuum. Pull the PRV to finish bringing the Brewbucket back to room pressure, you'll get some O2 ingress to the keg and assumedly the blowoff line but hopefully it'd be negligible.

I've heavily overengineered that and there is likely a flaw, such is the case after a six pack of 4 Pines Pale Ale in memoriam
 
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Kev R

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I use a filter housing with the filter removed, a stainless tube from the centre of the lid to the bottom of the housing.
The blowoff goes in top, forces starsan out the tube into a container. When crash chilled it reclaims the c02 from the filter housing and suckes the starsan back into tbe filter and not into the brew.
Not sure if putting the expelled c02 back in to the fementer is good or bad, doesn't seem to have caused any problem.
 

Danscraftbeer

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I dont understand how it could get sucked back? Easy solution is to pull the blowoff tube to above the waterline or just disconnect it at end ferment.
I pressure ferment btw. It only goes one way and that is out. Even when I've used a mini keg to collect blow off yeast its all one way. Disconnect if your worried about suck back.
I've never experienced this suck back scenario. :what:
 

fdsaasdf

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I dont understand how it could get sucked back? Easy solution is to pull the blowoff tube to above the waterline or just disconnect it at end ferment.
I pressure ferment btw. It only goes one way and that is out. Even when I've used a mini keg to collect blow off yeast its all one way. Disconnect if your worried about suck back.
I've never experienced this suck back scenario. :what:
It happens when you chill, and if you seal the stainless vessel you risk imploding it.
 

Bribie G

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As I posted in the OP, my worry is that if I just pull the tube out of the "airlock" fluid it's going to suck back air = oxygen.
 

Danscraftbeer

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I'm still confused as to how 500ml water gets sucked back into your brew?
All being in the same temperature control I cant understand how it could happen.
 

Brewno Marz

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Is there a number 4? No cold crash, just keg and accept the great, but bit cloudy beer, you've made.
 

Brewno Marz

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Implosion? Not an issue to consider.
Re- pressure ferment. It all goes out, nothing goes back in.
In a fixed volume the pressure is directly proportional to the temperature. So, reduce temperature and the pressure reduces. With a blow off tube or airlock the pressure before cold crash is atmospheric. Reduce the temperature and, provided the fermenter is sealed, you create a vacuum. Hence suck back of 500ml mineral water!
 

mofox1

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I'm still confused as to how 500ml water gets sucked back into your brew?
All being in the same temperature control I cant understand how it could happen.
Because it's not at a single temperature.

When you cold crash the beer, as in set the fridge temp to -1 or so, it will create a vacuum which will suck up the water.

I still use a dirty old plastic fermenter, and quite happy to bung a clamp over the blowoff tube once it's done. Yes, plastic has its advantages.

Edit: ah, just read you're a pressure ferment dude... As long as you have enough postive pressure at ferment temp to at least equal atmo at freezing, you're good. Not applicable for the OP tho.
 

Danscraftbeer

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Concur.
Its just that if you tune your process in the way that it only expels. Even cold chilling will never get to a vacuum. I'm a little confused here. Really 500ml sucked back?
:question:
 

mofox1

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Concur.
Its just that if you tune your process in the way that it only expels. Even cold chilling will never get to a vacuum. I'm a little confused here. Really 500ml sucked back?
:question:
Well, if you are not pressure fermenting, then **** yeah. You only chill after ferment is complete, and while there is some excess CO2 in solution, it's not enough to replace the volume that is lost due to cooling. Also note that the colder you get, the more soluble the CO2 is and less able to come out of solution.

So, If you have 10 - 20L of headspace, and about 50 to 100ml in your blow off tube, then the contraction due to temp is going to be a lot. Yes, 500ml a lot.

I'm sure there are calcs (ie ideal gas formula, PV = nRT) but I really can't be arsed with them. You cool stuff down, it gets cold. You cool a vessel with a headspace and it will implode if it's not strong enough to hold a vacuum.

As mentioned in a previous post, a phat assed blow off tube would help, as there is more volume in the tube... Although I'm guesstimating that it would need to be a couple inches dia to really be of use.
 

Black n Tan

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With a conical I just connect up the CO2 and give it a few psi, turn off gas and crash chill. However not so easy with your set up. How about just replacing the blow-off water with fresh boiled water and add a pinch of metabisulfite. That will minimise the O2 pick up. Better than sucking in air.
 

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