Back to basics - filling a 3-piece airlock

There's a lot of yap-yap on this forum about filling a 3piece airlock with miscellaneous *safe* liquids in case of a suck-back.

This post is to show how one can fill a 3-piece airlock that will only allow air (and not liquid!) to be sucked-back in the event that there's a pressure differential.

3-piece airlock:



Soak in a a bowl of sanitizer at least 4" deep:



Assemble the 3 piece while still covered in the sanitizing solution:



Up-right the now-assembled airlock, and pull it out of the sanitizing solution. The negative pressure will suck liquid out of the airlock, until it starts sucking air. At this point, it's not possible anymore for liquid to be sucked back.

It's a bit hard to take a picture of (because it happens under 2 seconds), but in this pic the water is draining from the bottom of the airlock:





And the result is a perfectly filled airlock with no possibility of liquid suck back:



Give a small shake to the airlock to release any liquid trapped in the stem.

Voila.

M_C

I keep looking at the last picture for the water level but all I can see is a bottle of Pliny.

If you can't figure out an airlock, maybe you shouldn't be playing with the stove/burner and hot liquids!

SwampassJ said:

I keep looking at the last picture for the water level but all I can see is a bottle of Pliny.

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It figures that the first reply would be about the bottle of Pliny in the background. Hard to get stuff in South Carolina!!!

M_C

Misplaced_Canuck said:

It figures that the first reply would be about the bottle of Pliny in the background. Hard to get stuff in South Carolina!!!

M_C

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Every now and then someone brings in a few bottles to the brew store and they share and sample but never when I can make it.

.

Try what I said about the carboy on the alcohol/airlock post using your method to fill the airlock (which is no different from any other method - the end result is exactly the same).

If you get no suck-back, then I stand corrected.

But I will ask again, do you cold crash?

ayoungrad said:

Try what I said about the carboy on the alcohol/airlock post using your method to fill the airlock (which is no different from any other method - the end result is exactly the same).

If you get no suck-back, then I stand corrected.

But I will ask again, do you cold crash?

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I cold crash all the time. No suck-back with the method posted above, as all the water that CAN be sucked back has already been sucked back. Only air can make it past the airlock (both in and out).

M_C

Someone on the other thread says that filling to the max line is overfilled and that will cause suck-back. Now, I can definitely buy that as an explanation for why some people get it and others don't. Your technique must result in a fill that is less than to the full line. This can also be easily accomplished by pouring a little less than usual directly into the outside of the airlock. I'll have to give it a whirl. Good to know.

I didn't think suck back was possible with a 3 piece airlock?
The airlock liquid level is below the top of the gas vent tube how can it get sucked into the fermenter?

Hello,
I just racked to my secondary and when I was securing my stopper/airlock, the spring water in the airlock sucked back into the carboy! I never removed the spring water from my stopper/airlock. So this was the same water that sat in the stopper for 2 weeks before the secondary transfer. I know there is nothing I can do about it now, but should I be worried about contamination?

BIGREDTRUCKER said:

Hello,
I just racked to my secondary and when I was securing my stopper/airlock, the spring water in the airlock sucked back into the carboy! I never removed the spring water from my stopper/airlock. So this was the same water that sat in the stopper for 2 weeks before the secondary transfer. I know there is nothing I can do about it now, but should I be worried about contamination?

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I think that all you can do now is wait and see. I fill my airlock with 100 proof vodka just in case something like this happens. Good luck!

Seems awfully complicated. All I do is spray with Starsan solution. Dump it. Fill the reservoir to the fill line with Starsan solution or vodka. Put the cap on then insert into the stopper.

I don't cold crash and have not had any suck back in 12 batches. I have had no infection problems either.

I don't mean to be an ass, but there is a perpetual flow of pliny available on tap where i live for four dollars a pint.

tonybus said:

I don't mean to be an ass, but there is a perpetual flow of pliny available on tap where i live for four dollars a pint.

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Very jealous. As far as I know, Pliny isn't even available in Michigan (if it is, I haven't found it yet!).

Im no pro, but seems by under filling or using the method stated In this thread that would allow only "air" to be sucked back into your fermenter rather than liquid completely renders the "air lock" useless... The whole point is to let air out and not let any air in... I second the use of Vodka as the liquid to use in your airlock... A little vodka getting sucked in won't hurt anything... A little potentially contaminated oxygen or what not in the air will...

dzlater said:

I didn't think suck back was possible with a 3 piece airlock?
The airlock liquid level is below the top of the gas vent tube how can it get sucked into the fermenter?

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Pressure differential. If the pressure inside the airlock is more than inside the carboy then the liquid will be pushed back into the carboy.

Qweegee said:

Im no pro, but seems by under filling or using the method stated In this thread that would allow only "air" to be sucked back into your fermenter rather than liquid completely renders the "air lock" useless... The whole point is to let air out and not let any air in... I second the use of Vodka as the liquid to use in your airlock... A little vodka getting sucked in won't hurt anything... A little potentially contaminated oxygen or what not in the air will...

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Keep in mind that if there's enough suck back, you'll run out of vodka and bring air in.

MC

Does anyone else not use an airlock? I used to use one but now I attach a blow off tube and just leave that connected until fermentation is complete. When fermentation completes the whole blowoff tube is full of CO2, it would take a lot of negative pressure to suck back all that CO2, the liquid in my mason jar and then start sucking air. It *seems* to me that using a blow off tube all the time would reduce your risk of suck back....but maybe there are other negatives that I amn't thinking about?

Seems logically sound to me. Minus possible risk of contamination in your blowoff water that might find its way back through the tube in the form of air?

HibsMax said:

Does anyone else not use an airlock? I used to use one but now I attach a blow off tube and just leave that connected until fermentation is complete. When fermentation completes the whole blowoff tube is full of CO2, it would take a lot of negative pressure to suck back all that CO2, the liquid in my mason jar and then start sucking air. It *seems* to me that using a blow off tube all the time would reduce your risk of suck back....but maybe there are other negatives that I amn't thinking about?

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I left a 1 gallon batch sitting on blowoff for 2 weeks while i went on vacation. I'd meant to rack it into secondary before i left but i had no time.

There was apparently enough variation in the weather while i was gone that when i got back, there was bleach solution sanitizer all up the hose to about an inch from the bend at the stopper.

I didn't think carefully enough before i started to deal with this situation. I should have slid the sanitizer bottle away from the jug until the end of the hose rose out of the water and then dumped back into it. Or something. I went to lift the hose out of the stopper and dumped a few fl of sanitizer into my beer.

So i dumped it.

Wow! All these problems with airlocks. I can't figure it out. I have lifted my Better Bottle and bucket, which both will flex, and got some bubbles in the airlock but got no suck back.

Maybe I'm doing something RIGHT, but I have never had any problem.

Also the 2 or 3 teaspoons of Starsan in my airlock would not worry me much even if it did get into the fermenter.

I use a blow off tube and always keep the catch jar at least as low as the bottom of the fermenter. Only about a cup of Starsan solution in there so you will never get a "2 gallons of Starsan in my beer" thread from me.

I have not gotten any liquid even starting back up the tube at any time even with severe weather in the area.

Maybe my time will come, or I have just jinxed myself, but I have never seen even the tiniest start of suck back. I dunno?

What can help as well when using better bottles is to use a milk crate or office file crate to carry the carboy in and out of the keezer. Not as much flexing of the better bottle which CAN draw in the water out of your airlock. As far as the way I do it when I cold crash, I use a solid better bottle stopper with the lip on it. Push it in to where its firm but not smashed way in there. No issues w/suckback because THERE's NO WATER to worry about. Make sure your bung is not too tight (hehehehhehe) or you may risk cracking the better bottle if too much of a vacuum builds up inside. Or just use sanitized aluminum foil.

Brilliant!
There is always a crazy ingenious dude who comes up with that kind of experiment.

I guess the point of this experiment is finding the ideal water level.

You could have tried with siphoning the airlock from the stem with your mouth.

That would be a bit grosser, but you could simulate a very strong pressure differential; and find the ideal water level.

I'll try with a bubbler airlock

BTW:

Chuck Norris is the only person to ever beat Andre the Giant in a drinking contest. And he did it by a two case margin.

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Is it some kind of urban legend?

The only problem I see with this is the airlock center piece slots being so close to the surface of the liquid,it'll let gas flow both ways. not a good situation. That's why I use cheap vodka in mine. nothing further to worry about. Start with a blow off & temps at the yeasts' lower range. when initial fermentation slows,re-install an airlock with vodka in it. A properly filled airlock allows gas to flow only one way;out. A low level like that will likely allow flow both ways without much provocation.

unionrdr said:

The only problem I see with this is the airlock center piece slots being so close to the surface of the liquid,it'll let gas flow both ways. not a good situation.

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That's the EXACT thing that is intended. To let a small amount of air in IF needed. Most of the time, the residual air will come from the fermentation anyways, as CO2 is heavier than air.

That's why I use cheap vodka in mine. nothing further to worry about. Start with a blow off & temps at the yeasts' lower range. when initial fermentation slows,re0install an airlock with vodka in it. A properly filled airlock allows gas to flow only one way;out. A low level like that will likely allow flow both ways without much provocation.

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There's nothing wrong with using vodka. It does evaporate a bit quicker than sanitizing solution though. I also don't keep vodka around the house.

MC

Misplaced_Canuck said:

That's the EXACT thing that is intended. To let a small amount of air in IF needed. Most of the time, the residual air will come from the fermentation anyways, as CO2 is heavier than air.



There's nothing wrong with using vodka. It does evaporate a bit quicker than sanitizing solution though. I also don't keep vodka around the house.

MC

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Well,the problem is that the airlock center piece doesn't always setle straifght down ime. It can settle kind of crooked,which could let air with nasties get sucked in. And in reality,some of that air is absorbed by the co2,not just layering.
I've used Starsan in my airlocks before,& when it bubbles,the sanitizer foams up & goes out the little holes in the airlock cap. The vodka in that respect lasts longer. It usually takes mine a week or two before it needs a top off. So it's not all that bad.
But the whole purpose of the airlock is to prevent air from getting in & bringing nasties with it.