Fermenting under pressure without a spunding valve

Sunfire96

Well-Known Member
Premium Member
Established Member
Joined
May 19, 2020
Messages
4,081
Reaction score
12,587
Points
113
Location
Virginia
I'm currently fermenting ~4 gallons of Golden ale with an OG of 1.047. It's currently at 1.017, it likely has another 5-10 gravity points to go. It's in a corny keg with the PRV removed for gas release.

What would happen if I put the PRV back on today? Would the last bit of attenuation cause pressure issues for the batch? If I remember correctly, the standard pressure for a keg PRV is way above typical spunding pressures, so I don't think it would harm the keg at all.

The keg is currently at 65F and I'll keep it there for several more days, maybe a week, to condition before lowering the temp steadily over a few days. Just curious about adding pressure at this stage in the ferment. Thanks!
 
Prv is usually set for 50-60 psi, aren't going to create a bomb, but it might get crazy carbonated, lol.

Most likely at that late stage of fermentation, won't be an issue.
 
My kegs have a 130 psi prv. The keg won't be harmed. High pressure makes yeast unhappy.
 
My kegs have a 130 psi prv. The keg won't be harmed. High pressure makes yeast unhappy.
But if fermentation is mostly done, isn't this when a spunding valve would be applied anyway?
 
Yes. By "high" I mean over 30 or so psi.

Maybe check it after it drops 5 points by a quick release if the prv, you will know if the pressure is 'too' high from the sound.
 
Yes. By "high" I mean over 30 or so psi.

Maybe check it after it drops 5 points by a quick release if the prv, you will know if the pressure is 'too' high from the sound.
That makes sense. 30 psi is about 2.5 vol of CO2 at 65F, which usually what I short for with carbonation. I've been trying to do some reading about how much CO2 is generated in relation to the gravity points/'Plato left to go but like so many other things with brewing there are values all over the place.

@Josh Hughes @Trialben @HighVoltageMan! I know you all pressure ferment. How quickly does the pressure build to your set spunding pressure? Is there a general rule of thumb you follow for when to apply pressure (for an ale)?
 
That makes sense. 30 psi is about 2.5 vol of CO2 at 65F, which usually what I short for with carbonation. I've been trying to do some reading about how much CO2 is generated in relation to the gravity points/'Plato left to go but like so many other things with brewing there are values all over the place.

@Josh Hughes @Trialben @HighVoltageMan! I know you all pressure ferment. How quickly does the pressure build to your set spunding pressure? Is there a general rule of thumb you follow for when to apply pressure (for an ale)?
Pretty quickly if fermentation is underway.
I feel it's a general consensus to not go over 15psi.
The idea is reduced esters through pressure and abilities to ferment warmer quickly and cleanly.
Dr hans pushes the boundaries on pressure fermentation check him out on the tube for his info.
 
this is what I've done in the past leave my keg in the house warm just pull the relief valve a couplie of times a day, leave it open if you have too
 
That makes sense. 30 psi is about 2.5 vol of CO2 at 65F, which usually what I short for with carbonation. I've been trying to do some reading about how much CO2 is generated in relation to the gravity points/'Plato left to go but like so many other things with brewing there are values all over the place.

@Josh Hughes @Trialben @HighVoltageMan! I know you all pressure ferment. How quickly does the pressure build to your set spunding pressure? Is there a general rule of thumb you follow for when to apply pressure (for an ale)?
Builds up quick. With a few points left I take mine off so I get a little extra co2. 10 points and it may be real carbonated. With my English ales I use an airlock lid until I have 10 left. Then set it at 15 psi (or what you need for your carbonation level) few points to go I take it off.
 
Think about it this way, if you were going to bulk carbonate, how much priming sugar would you need to add to get to your desired CO2 level?
3-4 ounces? Give or take.
And if you calculate out how many gravity points adding that much sugar would raise your gravity, you'll have your answer.
Most likely 1-2 points above your expected attenuation.
Much more than that, and you'll be trying to decarbonate your beer.
Hope that makes sense to you.
Cheers
Brian
 
Think about it this way, if you were going to bulk carbonate, how much priming sugar would you need to add to get to your desired CO2 level?
3-4 ounces? Give or take.
And if you calculate out how many gravity points adding that much sugar would raise your gravity, you'll have your answer.
Most likely 1-2 points above your expected attenuation.
Much more than that, and you'll be trying to decarbonate your beer.
Hope that makes sense to you.
Cheers
Brian
Thanks, that's a great point
 
If I’m at 15 psi with 1-2 left at 68 degrees then taking it off for the last 1-2 my carbonation is pretty much where I like it roughly 2 volumes of co2.
 
Thanks for the responses everyone. I guess I just need to get a spunding valve :) KegKing has a 15 psi PRV and 10 psi PRV that look interesting but they don't ship outside of Australia :/
 
Takes the worry away. The one I got was cheap. May not be accurate but it’s working how I wanted. It builds up fast so I’m finding it easier to make small adjustments to get it to the psi I want. @Craigerrr reminded me that if it pegs out past the last number in my case 15 then it can damage it.
 
Takes the worry away. The one I got was cheap. May not be accurate but it’s working how I wanted. It builds up fast so I’m finding it easier to make small adjustments to get it to the psi I want. @Craigerrr reminded me that if it pegs out past the last number in my case 15 then it can damage it.
That's partly why I want a valve that goes above 15, don't want to break it on accident and I like my beers at 2.5 vol of CO2

Just ordered the valve and some other goodies... :D
 
I’ll probably do that at some point. The 1-2 points with it closed is good for my British beers BUT you brew stuff that needs it a little more carbonated and consistent.
 
I put a spunding valve on a small batch of cider right from the beginning. Unfortunately, the spunding valve was assembled incorrectly where I purchased it and the pressure was going up to 30 psi. Once I figured out the problem (blowtie connected backwards) i have kept it at 12 psi. The next problem, I forgot it is still under pressure (almost 2 weeks). It's probably awful by now.
 
I put a spunding valve on a small batch of cider right from the beginning. Unfortunately, the spunding valve was assembled incorrectly where I purchased it and the pressure was going up to 30 psi. Once I figured out the problem (blowtie connected backwards) i have kept it at 12 psi. The next problem, I forgot it is still under pressure (almost 2 weeks). It's probably awful by now.
Why would it be bad?
We keep beer and cider carbed indefinitely.
 
You're right but it is still sitting on the yeast and I may have over pitched the yeast. I'll check it out when I get home from work tonight.
It will be fine lotta people ferment under pressure and never racket off and just drink it right out of a keg or uni tank or whatever they have it here
 

Back
Top