So I get why air needs to revert back in to the carboy or bucket as the beer cools to lagering temps. But when the beer is at lagering temps, why is my blow off tube still sucking in water? I have to release the pressure every couple of hours.
Dave
Is the beer still cooling or at stable temp?
- Sent by my R2 unit
Beer is at stable temp Jimmy. That’s what I don’t get.
If negative pressure is still buildingin the carboy then the beer is not yet at stable temp.
Mort, the bucket with the temp probe has been stable for 2 days, yet still has some negative pressure. Could it have anything to do with the yeast storing up for hibernation?
Edit: There are 3 buckets in the chest freezer…
Total shot in the dark here
Could the negative pressure build to a point where the bucket looses its seal allowing new air to come in? The the new air compresses further sucking more liquid up the blowoff.
Hmm. If the air is the same temp in the chest freezer, would that make a difference? I don’t know.
Here’s another theory, if the fermenter is in a fridge then when you open the door you let out the greater-than-ambient air pressure which was keeping the pressure equalized when the door was shut.
I just made that up, but it almost makes sense.
It makes sense to me. The only thing is that after time like 3-4 days it finally equalizes. I just checked and the water was only sucked up about an inch instead of halfway to the bucket as before.
Bumping this to get some of the experts opinions. I’m thinking it’s yeast related but would really like to understand this. I lost a lager this summer because of blow off water getting sucked back in the fermenter. I use vodka now but that evaporates quickly. Was thinking about switching to cut down air locks as my freezer is a tight fit for buckets. Only a few inches of head space which is why I use blow off tubes. I’m in a quandary! :o ???
EDIT: No offense to the other experts that already replied… 
No offense taken. I’m not sure what else it could be though. If liquid is moving up the blow off tube it is because the pressure out side the bucket/blow off system is greater than that inside. Could be temp drop inside, could be a leak in the bottom of your bucket, could be atmospheric pressure changes. After all you have essentially built an atmospheric pressure meter.
Can’t help you with why it’s happening but using an S airlock instead of a blow off tube will help prevent the liquid from sucking back in.
+1
+1. Or lager in a corny.
Or use a solid lid/stopper.
If I had to guess I would say its because the solubility of gases increases as temperature decreases. As the beer cools to lagering temperatures, more of the gas in the headspace will disolve into it. Every time you burp it, you let in more gas, increasing the head pressure. This should equalize after a few days as you have observed.
Rather than using a solid stopper, which might blow out once the CO2 produced by the fermentation gets going, I would suggest a silicone stopper that burps as CO2 is produced.
As to the pressure dynamics, I really don’t know, but I try to get the wort below pitching temperature before pitching (and imposing an airlock or blowoff tube) and this allow for a slight rise in temperature from that point, so I have not experienced the dreaded “suck back” at least not to levels that are noticeable to me.