I would like to start leaving beer and mead in secondary at a location that I may not be able to get to on a regular basis (sometimes not for several weeks) and have a few questions for anyone who might know the answers:

  1. How long will a normal 3-piece or s-shaped airlock remain full of water and "useful" with no supervision. I know that humidity and temperature will play a factor but does anyone have any experience on how long it has lasted for them before drying up?
  2. Aside from setting up a blow off tube into a big jug of water does anyone know of any alternatives to a standard 3-piece or s-shaped airlock that would last a longer time? Sure the blow off set up will work fine but I'm hoping for something a big more "elegant"

Thanks in advance for any advice you can offer.

  • I will put my word here since it does not answer your questions directly, but there is my advice: If you will set the fermentors and them go away, I don't recomend to use a "elegant" airlock. The fermentation can be vigorous and you could end with a clogged airlock rocketing out of your fermentor, beer everywhere, big mess, etc. Or the liquid could just dry as you are saying. So I really think that a blowoff tube could be safer to leave alone. There is some things that could make it feel more 'elegant' than just a hose coming out of the fermentor. – jards Jan 21 '15 at 16:54
  • Sorry, I've missed the part where you states that you'll doing only secondary fermentation this way... So forget about my advice. What kind of fermentors you will use? – jards Jan 21 '15 at 16:54
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    @jards I use a Better Bottle for secondary. – Michael Jan 27 '15 at 19:33

Question 1 is hard to answer because its so dependent on the relative humidity and air flow of the room in question. I wouldn't assume an airlock with water would be safe for more than 4 weeks without checking on it or topping it off.

Vodka is sometimes recommended as an airlock liquid, but I think its is a bad idea for long-term storage. Being roughly a 50/50 mix of ethanol and H2O, its going to lose a considerable bit of its volume as the ethanol evaporates. Your airlock is NOT air-tight (despite the name) so this evaporation is not easily preventable. Also, ethanol is a weird form of sugar and can attract some kinds of hardy bacteria. Leave a glass of whiskey out exposed for a few days and you'll notice that SOMETHING from the air is chomping away at it.

I would go with food-grade glycerin, sold at pharmacies. It won't evaporate and is harmless if a little gets sucked back into the fermentor if the temps drop (its used to add a little "body" to wine so it might actually improve your beer/mead).

Here's a good thread on the subject.

  • +1 : for the glycerin idea (both to battle evaporation and as a potential body-enhancing additive). – Henry Taylor Jan 21 '15 at 15:14
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    Thanks @Graham, I had never heard about using Glycerin before. I will def. check this out. – Michael Jan 27 '15 at 19:35
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    when you mentioned glycerin (a common ingredient in e-cigaret juice) made me think of another alternative, propylene glycol. It is a common food additive, however it is toxic (dangerous only in large quantities) and should prevent bacteria growth in the air lock. – BenCamps Jan 28 '15 at 22:37

I don't think water would remain useful for very long at all. It will stagnate and become fertile ground for lots of little nasties.

I recommend filling your airlock with cheap vodka. The alcohol will prevent microbes from growing in the liquid for a long time. As long as your airlock is properly capped, it should be fine for several weeks, and probably several months. The only time I ever had an issue was with an airlock that I (inadvertently) filled with a flavored vodka. After a few months, I'm guessing the alcohol dissipated enough for the flavored sugars to become a Petri dish! :(

The S-shaped airlocks have less surface area and therefore are subject to less evaporation. However 3-piece or S-shaped are not ideal during initial fermentation when blowoff is possible. I also wouldn't recommend leaving a brew for several weeks during this phase, either.

  • I should have clarified that I never use just plain water, I always use water & starsan. I wonder which (between vodka and starsan) would evaporate less quickly. I agree that the s-shaped airlock has less surface area but it seems to me that it also holds less liquid. You really think vodka would last several months? – Michael Jan 21 '15 at 3:36
  • Vodka keeps essentially indefinitely when it's sealed it the bottle. – djs Jan 21 '15 at 6:23

There is a variant on the "blow off into a separate jug" approach, which involves placing your entire fermenter in a water-filled container (a pail or tub) to provide temperature stabilization and then run the blow off tube down into that water. Basically getting two functions out of a single tub of water.

If you found a tub with a diameter just slightly larger than the exterior of your fermenter and if you strapped the blow off tube in tight against the fermenter, the whole could be considered a single unit.

--- Edit : Another Idea ---

You could modify a standard 3-piece airlock by extending the outer tube with transparent plastic pipe from an aquarium store. By making the airlock 4-6 inches tall, it could hold more water/vodka/sanitizer which would then take longer to evaporate away.


I have used the normal 3-peice with water for years to make wine and several of the wines I make have to sit in the secondary for 1 1/2 months between racks. I have never lost more that 1/2 of a safe amount of the water and have never had to top it off. But, I keep my wine in a stabile / controlled environment.

If you are worried about your environment, you can do what many home brewers (and I imagine even larger brewers) had done for a long time before helpful inventions like the 3-peice or s-style. Run a hose out of the top of your carboy into a glass / pail / drum of your favorite liquid. I am sure you can find something you can fill that will not entirely evaporate.


I use clingwrap, secured by a heavy duty rubber band. I punch two pin holes in the wrap to ensure excess CO2 can escape. Not very elegant, but very effective!

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