Been tying myself in knots over this one... I'll actually try plan A and just attach a bag to the end of the tube to fill with CO2 and see what happens, will post pix. I'm using the San Diego Super Yeast again, pitched Thursday so I'll be on the lookout Sunday pm.
Blowoff Suck Back
- Thread starter Bribie G
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hotmelt
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Why not take the poppet out of a carb cap,attach it to your blow off hose,then squeeze the air out of your bottle and screw on to carb cap.
Gelding
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I also had this problem. Actually its a good problem to have, because it means that your fermenter can hold pressure if needed (eg fermenting under pressure if thats what you want to try, but its another story).
I solved it two ways.
1) instead of a liquid receptacle, just cover the end of the blowoff tube with tin foil so nothing can crawl up there (even if it did, co2 would ensure limited progress) remembering that during active fermentation you have positive pressure so the flow direction is out. When you cool or crash, you will suck back a bit of air but noticed no deletirious effects on my beer. But sucking back air is batter than spring water (or starsan!)
2) if you are concerned about air and possible oxidation, the more anal way is to pressurise your fermenter with co2 before chilling. you could do this because your fermenter can hold pressure. after fermentation is complete and before you chill, blow into your fermenter around 15 to 20 psi of co2 and seal. You will need to modify your outlet to include a small valve to achieve this though.
I solved it two ways.
1) instead of a liquid receptacle, just cover the end of the blowoff tube with tin foil so nothing can crawl up there (even if it did, co2 would ensure limited progress) remembering that during active fermentation you have positive pressure so the flow direction is out. When you cool or crash, you will suck back a bit of air but noticed no deletirious effects on my beer. But sucking back air is batter than spring water (or starsan!)
2) if you are concerned about air and possible oxidation, the more anal way is to pressurise your fermenter with co2 before chilling. you could do this because your fermenter can hold pressure. after fermentation is complete and before you chill, blow into your fermenter around 15 to 20 psi of co2 and seal. You will need to modify your outlet to include a small valve to achieve this though.
Jack of all biers
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Bribie, I saw a post a few weeks back where someone did exactly that. The bag (medical plastic thingo) was connected between the blow off and the water/sanitizer solution. The bag fills with CO2 first, holds pressure and when the cold crash pressure drop occurs only the CO2 from the bag is sucked back stopping o2 and water getting back in.
Has to be able to hold pressure and be big enough to act as a gas reservoir for the change in volume.
Wish I could link you the thread, but on phone and can't remember what it was titled. As I said though it was only a few weeks back I saw the post.
EDIT- there was possibly a plastic valve on the bag to ensure water wasn't sucked back, but can't remember.
2nd EDIT - Ha. On my PC now and a quick search and here it is https://aussiehomebrewer.com/threads/preventing-cold-crash-suck-back-in-fermenters.96165/
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Lyrebird_Cycles
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The easy solution is to make the tube longer. Assuming your ferment is at 15 - 20 oC, the suckback volume when cold crashing is at most about 15 % of your headspace volume*. Make sure your tube is long enough to accommodate more than this volume and you are gold.
* This assumes that the reduction in pressure though the equilibrium shift due to the increase in solubility of CO2 at the lower temperature is too slow to be important.
* This assumes that the reduction in pressure though the equilibrium shift due to the increase in solubility of CO2 at the lower temperature is too slow to be important.
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mofox1
Wubba lubba dub dub!
My math might be bad, but 1m of 10mm dia tubing is ballpark 100ml...
If I have 10L of headspace, that's 1.5L volume reduction. I'd need 15m for 15L headspace! Or much fatter tubing... ~30mm dia to get it in 2m.
Starting to think that having a CO2 suck back bag might not be a bad idea.
Black n Tan
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Yer your maths is out 10-fold. 1 meter of 10mm ID tube will hold 785mL. So you need about 2 metres for 1.5L.
Edit: 1 meter is 78.5mL
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mofox1
Wubba lubba dub dub!
http://www.handymath.com/cgi-bin/cylinder.cgi?submit=Entry reckons 78ml for 1m of 10mm dia tube.
Black n Tan
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Right you are, my mistake.
Danscraftbeer
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I like the idea someone already mentioned to use a carb cap on the blow off bottle with dip tube to the bottom of the bottle. Have the cap loose when in active ferment is the same as what he has now. Ideally a 2 or 3lt bottle. You really dont need any water in it either since the bottle gets well and truly purged with co2. Near end of ferment, prior to cold crash tighten the carb cap so the bottle will become pressurized. That's instead of stuffing around and swapping to a co2 balloon bag etc. The bottle will collapse when it chills down.
Reason I pressure ferment is because of the bonus advantages of using your brews own produced co2 saving on bottled co2 and a fair bit of messing about as well.
$0.02
Reason I pressure ferment is because of the bonus advantages of using your brews own produced co2 saving on bottled co2 and a fair bit of messing about as well.
$0.02
Lyrebird_Cycles
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Yes that's more headspace and thinner tubing than I'd reckoned on. The bag is probably easier.
With the brew bucket I use a very thin tube as it fits into the drilled plug that came with the BB. I'll measure the ID and do a quick pie arrh squared aitch calculation and see how much I'd need. If kept as a neat coil it shouldn't be unwieldy and not really expensive - LHBS and BCF sell a range of tubing.
DJ_L3ThAL
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What do commercial breweries do? They'd have large temp swings when say the glycol system kicks into gear that would multiply out to a decent volume of 'suck back'. I've seen a couple and from memory the internal diameter was no greater than 1 inch (25.4mm) and a FV height of 3m, which is is approx 1 litre of hose volume.
How much volume change could a 2000L FV have? Even a 1 degree swing with no active ferment at the time would result in more than 1L volume change wouldn't it?
How much volume change could a 2000L FV have? Even a 1 degree swing with no active ferment at the time would result in more than 1L volume change wouldn't it?
nosco
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I think I read on here some where that you can fit a 1/2" silicone hose straight in to the top of the BB lid which might help, I dont know how. Ive also seen people put a hose over the inside tube on a 3 piece air lock as a make shift hose adapter. The valve on my 20lt collapsible water container (that ive never used) has a 10mm OD on the outlet.
I have been swapping the blow off with an air lock after the main ferment is done but that introduces O2 of course. I think I might try this next time I use my BB. I have been using a blow off tube all the time now with my BB as I always get "blow off". I am probably over filling a bit.
My only concern with the collapsible container would be cleaning it. It is clear though so it shouldnt be a problem.
I have been swapping the blow off with an air lock after the main ferment is done but that introduces O2 of course. I think I might try this next time I use my BB. I have been using a blow off tube all the time now with my BB as I always get "blow off". I am probably over filling a bit.
My only concern with the collapsible container would be cleaning it. It is clear though so it shouldnt be a problem.
Cleaning it shouldn't be a problem since it's only being used once the vigorous fermentation has subsided and it's just capturing the co2.
Another option would be to fill it with co2 from your bottle and only attach it to your fermenter when you're ready to chill.
I've ordered a couple, keen to try it.
Another option would be to fill it with co2 from your bottle and only attach it to your fermenter when you're ready to chill.
I've ordered a couple, keen to try it.
Lyrebird_Cycles
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Commercial breweries have pressure regulators and vacuum breaker valves on the tanks so suck back doesn't occur. You'd need -30kPa of vacuum to suck back on a 3 metre line.
DJ_L3ThAL
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Rightio! Do the vacuum breaker valves just let air in? (Albeit a small amount proportional to the headspace).
Back on HB scale, the water bladder or simple spring water bottle are good ideas. Anyone know of a PET bottle cap that has a 9mm or 12mm hose tail/barb on the outside as well as inside? Or could just use a carbonation cap and a quick disconnect. Think I even have the fittings for the latter and an adaptor for my Chronicals with John Guest push fitting so I can supply CO2 when kegging/bottle to avoid air ingress.
Matplat
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What about having an intermediate vessel to increase the volume of your blowoff line? Then the water would just fall into the empty intermediate vessel, and you'd just have to be sure you have enough water in the air lock bottle so that only water gets drawn through, not air.
A bit more cumbersome, but simpler I think?
A bit more cumbersome, but simpler I think?
earle
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Simpler is better for a blow off arrangement I think. It's one thing to think about gas being blown off but once you add some krausen into the mix I reckon some of the suggestions could get a blockage.
What about running the blowoff tube into a 3 or 4L pet bottle with say 500ml liquid in the bottom. Drill a hole in the cap of the blow off bottle just large enough so that your blow off tubing can form a seal (maybe a bit of keg lube would help get a good seal or add a grommet if this doesn't work). During ferment have the end of the blowoff tube in the liquid and the lid of the bottle slightly loosened to release excess pressure, but still retain co2. When you cold crash, withdraw the tube from the bottle but not completely so the end is just below the lid. Tighten the lid so that air is not drawn into the bottle. As your fermenter cools and creates a vacuum, it should draw in co2 from the blow off bottle but not liquid, and the bottle can collapse in
What about running the blowoff tube into a 3 or 4L pet bottle with say 500ml liquid in the bottom. Drill a hole in the cap of the blow off bottle just large enough so that your blow off tubing can form a seal (maybe a bit of keg lube would help get a good seal or add a grommet if this doesn't work). During ferment have the end of the blowoff tube in the liquid and the lid of the bottle slightly loosened to release excess pressure, but still retain co2. When you cold crash, withdraw the tube from the bottle but not completely so the end is just below the lid. Tighten the lid so that air is not drawn into the bottle. As your fermenter cools and creates a vacuum, it should draw in co2 from the blow off bottle but not liquid, and the bottle can collapse in
