Size does matter in spite of what she said at the LHBS

[Bubbles2]

So I have about 30 odd batches under my belt, still learning. And this morning I learned that size does matter. I have been using a BMB (big mouth bubbler) with a 3 piece airlock. Thinking that it is a bit more complex (looking) and has the ability to hold more Star San in it...Turns out, when I had thought that after 10 days of Primary Fermenting the Wort is now Beer and ready to bottle.. Due to no activity.
Not so fast... After the usual 10 days I went to check on my Slutty Blonde Brew and realized that my larger 3 piece unit had a slight crack in it, upon this discovery I thought well let me switch it out until I can "get to it" with a "back-up" or "Throw down" if you are a LEO...LOL and low and behold there is still slight activity with the 1 piece Unit....

So I am now a believer in the one piece albeit a smaller unit, (as far as liquid retention goes).
I may still use the larger one with more Star San retention and a Larger express burper for start, but will always switch to a smaller one piece the last 5 days or after the Krausen has fallen.
So for now my Slutty Blonde is not ready for me, she is still burping, albeit minimal.

 

[Hoppy2bmerry]

The thing about the S airlock is it will still serve its purpose even with a small amount of fluid... great for bulk aging in dark forgotten places, and risk of “suck back” from cooling is extremely low.

 

[RM-MN]

So I have about 30 odd batches under my belt, still learning. And this morning I learned that size does matter. I have been using a BMB (big mouth bubbler) with a 3 piece airlock. Thinking that it is a bit more complex (looking) and has the ability to hold more Star San in it...Turns out, when I had thought that after 10 days of Primary Fermenting the Wort is now Beer and ready to bottle.. Due to no activity.
Not so fast... After the usual 10 days I went to check on my Slutty Blonde Brew and realized that my larger 3 piece unit View attachment 631462 had a slight crack in it, upon this discovery I thought well let me switch it out until I can "get to it" with a "back-up" or "Throw down" if you are a LEO...LOL and low and behold there is still slight activity with the 1 piece Unit....
View attachment 631461
So I am now a believer in the one piece albeit a smaller unit, (as far as liquid retention goes).
I may still use the larger one with more Star San retention and a Larger express burper for start, but will always switch to a smaller one piece the last 5 days or after the Krausen has fallen.
So for now my Slutty Blonde is not ready for me, she is still burping, albeit minimal.

The bubbling or burping is not a sign that fermentation is still going on, it is a sigh that there is an exchange of gasses. That's all. To tell if your beer is done or still fermenting you need to use your hydrometer.

Beer can dissolve an incredible amount of CO2, much more than it can hold long term. When it releases some of it, the airlock bubbles. This can continue for several weeks, much past the end of the fermentation.

 

[Bubbles2]

For this example the 3 stage had no activity for minutes on end, the single is now giving a burp every 5 seconds. I like to wait till there is no activity, opposed to opening the vessel introducing o2 and wasting 7oz of beer to measure it.
When there is no activity I get to it in a couple of days, leaving it on the cake till then. When I state no activity I mean no bubbles for a few minutes or even longer, even though as you state it could be an exchange of gasses.

 

[RPh_Guy]

S-shape airlock: Zero risk of [liquid] suckback if filled appropriately. Easy to maintain full (easier to see, less evaporation compared to 3-piece).
Available in glass, which is less oxygen-permeable.

3-piece airlock: Easiest to clean. Blow-off tube can attach directly (I'm not sure that's an advantage). High risk of [liquid] suckback and can run dry relatively fast.
In my experience, more sturdy.

Waterless/ breathable airlock: No sanitizer needed; no risk of running dry. Possibly more oxygen-permeable, depending on material. Less noisy. Lowest profile. Zero suckback ever, including no air suckback, which prevents oxidation. However, leaks are harder to detect.

 

[Alex4mula]

Waterless/ breathable airlock: No sanitizer needed; no risk of running dry. Less oxygen-permeable, depending on material. Less noisy. Zero suckback ever, including no air suckback, which prevents oxidation. However, leaks are harder to detect.

Any pictures of these?? I like the 3 piece but they are fragile. If I drop one it usually cracks. How can an S type has no suck back if it can have suck out??

 

[RPh_Guy]

Any pictures of these?? I like the 3 piece but they are fragile. If I drop one it usually cracks.

I have a bunch of these:
https://www.morebeer.com/products/carboy-bung-silicone-breathable-10.html and
https://www.morebeer.com/products/carboy-bung-silicone-breathable.html
They're really awesome except the silicone is oxygen-permeable, so you need to package the beer quickly after fermentation ends. Taping some foil over it might help.
They're extremely durable and can be boiled to sanitize.

I'm currently testing a DIY breathable airlock using a bottling wand valve inserted into a drilled stopper... With a little silicone lubricant spray to ensure a good seal. I can put some liquid in it to make sure it doesn't leak.

How can an S type has no suck back if it can have suck out??

When I said no suckback I meant no liquid suckback.
Edited my previous post for clarification.