S-type air lock modification for ferm chamber

[RobMull53]

Wondering if the attached image of an s-type air lock modification would work. I get by pretty good with DIY engineering, but not so much with physics. (and as I'm getting started with brewing, working on warming up to chemistry too). I'm ready to move to fermentation temp control, and i'm trying to work with what I have: 5 gal glass carboys, and a spare small fridge (apartment size - tiny freezer within). Plan to get a Ranco two stage controller in case I ever need to heat. This fridge seems like a good candidate to me because I thought I'd check its performance and see how low its own controls would bring a container of water in the fridge section - it froze solid. So to point: The top of a three-piece air lock just about touches the bottom of the freezer section. I'm thinking I should use an s-type if I ever lager, but it will not fit, unless the idea in the attached image would work.

Feel free to suggest alternate solutions like a shorter ferm container (plastic barrel type, hand-blown big mouth glass type), or just always use the three-piece even at very low temps. I did look into these questions, but didn't come away with a strong conviction either way.

 

[Pscdouglas]

Search for Blowoff tube and see some pics. You don't need the "S" if you just end your tube in a vessel with some fluid, you could put it on the floor of the chamber next to your fermenter.

 

[PGEduardo]

With a ferm chamber, you shouldn't be opening it much and won't have tons of drafts. I have just covered the top of mine with tinfoil (try to get it into a keg or bottled ASAP). Other people just use plastic bags or rubber gloves rubber-banded to the top (just make sure to poke a small hole to relieve pressure).

Don't be married to a single airlock type. 3 piece is fine. If you cold crash just take the airlock out and cover with plastic or something...

 

[RobMull53]

I always start with a blowoff, then switch to a 3 piece. Once I tried a Belgian golden strong and it was in my main fridge around 35 for weeks at the tail end, and my little bit of research caused me to believe a s-type is better at those temps because of the possibility of drawback. I used one, but didn't notice any vodka being drawn out. I guess I'm stuck on the theory about the advantage of the s-type, but as noted, I'll look into the wrapping/covering technique.

 

[p_p]

Wondering if the attached image of an s-type air lock modification would work. I get by pretty good with DIY engineering, but not so much with physics. (and as I'm getting started with brewing, working on warming up to chemistry too). I'm ready to move to fermentation temp control, and i'm trying to work with what I have: 5 gal glass carboys, and a spare small fridge (apartment size - tiny freezer within). Plan to get a Ranco two stage controller in case I ever need to heat. This fridge seems like a good candidate to me because I thought I'd check its performance and see how low its own controls would bring a container of water in the fridge section - it froze solid. So to point: The top of a three-piece air lock just about touches the bottom of the freezer section. I'm thinking I should use an s-type if I ever lager, but it will not fit, unless the idea in the attached image would work.

Feel free to suggest alternate solutions like a shorter ferm container (plastic barrel type, hand-blown big mouth glass type), or just always use the three-piece even at very low temps. I did look into these questions, but didn't come away with a strong conviction either way.

I use exactly what you've shown as otherwise the FV doesn't fit the fridge. Works just fine. Go ahead.

Edit, I always have enough head space as I brew in a bucket. I guess that's the caveat. Good luck.

 

[MagicMatt]

I always start with a blowoff, then switch to a 3 piece. Once I tried a Belgian golden strong and it was in my main fridge around 35 for weeks at the tail end, and my little bit of research caused me to believe a s-type is better at those temps because of the possibility of drawback. I used one, but didn't notice any vodka being drawn out. I guess I'm stuck on the theory about the advantage of the s-type, but as noted, I'll look into the wrapping/covering technique.

Your concern is well founded, but for the wrong reasons. There is no advantage to using the S-type airlock. The S-type (commonly called a 2-piece) is not any less susceptible to draw-back than a 3-piece. And actually the 2-piece may technically be worse for drawback conditions because they do indeed differ in how they behave in a cold-crash situation though:

- A 2-piece airlock will likely not suck back any liquid from the airlock because of its shape. But what this means is that it will essentially work in reverse from its design; that is, it will pull air from outside through the s-lock, bubble through the liquid and suck that air into the fermentor. This is introducing oxygen to your beer, and is a huge no-no.

- A 3-piece airlock will likely begin to suck back the liquid in the airlock before it allows air into the fermentor. If the reason for the suck-back is just due to a minor swing in temps (within 5°F), then there is little cause for concern; after all, it's just a bit of sanitizer or vodka, neither of which will hurt your beer. However, if the reason for the suck-back is because you're cold crashing, then this airlock will also start to suck in air (oxygen) once it's sucked in all of the liquid. Obviously, you want to avoid this situation as well.

So basically you should be looking for another alternative to either of these airlocks for cold crashing purposes. Personally, I use a solid bung stopper (remove the airlock altogether) when cold crashing. This will still create a negative pressure in the carboy, but it will not suck in anything until I pull the bung (at which time a whoosh of air rushes into the carboy). But since I only do this right when I'm about to keg, there is only a few minutes of contact time with the oxygen and no need to worry really.

If you don't want to worry about switching the airlock for a stopper, look into the BetterBottle DryTap. It's a one way dry airlock that will let positive pressure out, but stops anything from going in when there is negative pressure.

 

[RobMull53]

Everyone:

thanks for the input.

MagicMatt:

Your full explanation in your post was very clear.

About a stopper, you said...

"Personally, I use a solid bung stopper (remove the airlock altogether) when cold crashing. This will still create a negative pressure in the carboy, but it will not suck in anything until I pull the bung (at which time a whoosh of air rushes into the carboy)."

I like this method.
I will be wanting to use a stopper that holds a thermowell...

Any reason you use a bung instead of hood/cap type?
I assume the bung stopper you use is NOT the cup-shaped kind called universal?
Hard to pull out?
Worst case scenario - can it be drawn all the way down in?
What size for a 5gal glass carboy?

 

[MagicMatt]

Any reason you use a bung instead of hood/cap type? I assume the bung stopper you use is NOT the cup-shaped kind called universal?

If you mean one of these, the reason I do not use them is that they are not air tight. In fact, they are some of the worst offenders when it comes to letting air into the carboy. Check out this study that measures the level of O2 permeability via different types of bungs/caps and airlocks.

I generally use one of these (on the left) or one of these. They each have their trade offs. The first one is more permeable to oxygen than the second, but it's also easier to pull out. Which leads to....

Hard to pull out?
Worst case scenario - can it be drawn all the way down in?

It's not "hard" but it does take some elbow grease. I've never thought it wasn't going to come out or anything, but you do have to work it out a bit. That's why I kind of prefer the first type I linked, because it has a lip that both prevents it from going in too far (which, while it hasn't happened to me for the other type, it seems more possible), and it helps get a good grip to wiggle it out. Once you break the seal and air starts to creep in and relieve the pressure it becomes much easier.


Another option if using a 5 or 6 gallon carboy is to use one of these carboy caps as they are listed in the above study as essentially impermeable to O2, and then either a PET solid rod (see the study) or one of the BetterBottle Dry Taps. It will create an air tight seal, and it's much easier to pry the rubber cap off of the neck of the carboy this way. It doesn't work with the fatter 6.5 gallon carboys though as the outer diameter of the neck is just slightly narrower and it doesn't create a good seal.

 

[MaxStout]

Another option if using a 5 or 6 gallon carboy is to use one of these carboy caps as they are listed in the above study as essentially impermeable to O2, and then either a PET solid rod (see the study) or one of the BetterBottle Dry Taps. It will create an air tight seal, and it's much easier to pry the rubber cap off of the neck of the carboy this way. It doesn't work with the fatter 6.5 gallon carboys though as the outer diameter of the neck is just slightly narrower and it doesn't create a good seal.

I use those big rubber caps, with great results. Morebeer has them for about $4. You're right, they tend to fit a bit loosely on 6.5 gal acid carboys, but I use a hose clamp to seal it up better. They fit nice and snug on 3, 5 and 6 gal carboys.