Carbonating Beer in Small Breweries

Carbonating beer in small breweries comes up a lot, with people who reach out to me for brewing advice. Brewers wanting to know how to properly carbonate beer consistently.

Well, I had another enquiry this week from a lovely guy called Norman. He wanted to follow-up on the article I wrote about how to spund beer for natural carbonation.

Unitanks Pros and Cons - Spunding

He gave me permission to share the email conversation we had. Please note, for this article 15 PSI (pound per square inch) is approximately 1 Bar.

His Initial Emil Read – Carbonating Beer in Small Breweries

Hi Neil

I’ve been reading your articles about carbonation stones and spunding valves and found them really interesting.

I went from home to commercial brewing last year. I’ve a 2.5bbl plant and 3 unitanks. I’m brewing British real ale in South West France. I have a tap room and several commercial outlets.

People seem to like the product (I brew 5 different ales). I am however, not completely happy with the carbonation level at bottling and had a few bottles returned.

I open ferment the primary fermentation at around 22c. Then chill down to 4c, add syrup and finings and seal the fermenter for the secondary fermentation. I then chill down again to 4c for kegging and bottling.

Carbonating Beer in Small Breweries - FV's
One of Norman’s Unitanks

Kegging My Beer

I use 19L corny kegs and run the beer directly from the racking arm into open kegs (the beer is only open to air for the length of time it takes to fill the kegs, approx. 2 mins). Once filled they are sealed and co2 put on top at around 1 bar.
For bottling, it’s then transferred from keg to a manual bottling machine using co2.

Manual Beer Bottle Filler - Overview
Norman’s Bottling Machine

I don’t want fizzy beer, but it needs to be better than it currently is. From keg in the Tap Room, it’s served at 10c at 1 bar pressure and is perfect.

I was thinking of getting a carbonation stone, but the idea of natural carbonation is much more appealing. If I go down the route of spunding though, can the primary fermentation be done under pressure with ales?

Also, at the end of the primary when adding syrup and finings, I would have to open the vessel. Just trying to get my head round it all and find a better way forward.

Carbonating Beer in Small Breweries – My Response


Thanks for your email and it’s always nice to hear from a fellow brewer. There’s a lot going on in this email. It might take a few messages to get this down. I need to have a better idea of your tank set up first.

1. The complete FV – if you have drawings from the equipment manufacturer even better.

I’ll need some pictures of your tanks, I need to know how the FV looks please. It seems to have two outlets (drain and racking arm).

It sounds like you’ve a traditional unitank, because you can seal up the FV for building CO2 during secondary fermentation. So, in theory if the unitanks look how I think they do, you can spund the beer. With the purchase of spunding valves.

2. Are you dry-hopping any of your beers?

If you are, then you can’t spund your beers, really. It of course depends how you add your dryhop, you may experience a dry-hop volcano under certain (most) conditions.

This is what a dryhop volcano looks like!

Furthermore, you can only get head retention once so, any CO2 breakout and foaming is less than ideal.

Please tell me your current dry-hop technique…

Do you add before terminal gravity?

Do you drop the temp at all for dry hop?

The more of the process you explain, the better I can help you.

3. How long can you leave the beer in tank? What PSI can you hold your tank at?

With your system and 5 beers, I’m guessing you need quick turnaround time. In theory if you’ve time, you can keep topping up CO2 after the dry-hop, with the beer will slowly carbonating.

If you don’t dry-hop a beer, then you can begin to spund once the beer has started fermenting. I usually begin spunding once the beer has dropped 2 Plato points, or so.

Also, what’s the maximum working pressure of your unitanks? The higher the pressure the quicker the beer can absorb CO2 and become carbonated. Also, it worth noting the colder the beer the quicker it’ll carbonate too.

4. Adding sugar to the beer after primary.

If you spund the beer or let it carbonate naturally over time, then you don’t need to add sugar for secondary fermentation to add CO2

I’ve attached a video (see below) of the setup I use, when I want to add finings if a tank is under pressure. With this set up I can push finings or a sugar solution into a tank using CO2 at a higher pressure, than the tank is at.

Then with finings; I recirculate the beer for 20 minutes minimum, to properly mix in the finings in. Primary fermentation can be done under pressure with most beer except:

1. Beers you intend to dry-hop

2. Beers where a lot of the character coming from the yeast (e.g., saison). Fermenting under pressure can mute the character given by the yeast (phenolics of a saison yeast, for example).

There may be other beers (you don’t want to spund), but I’m answering this email first thing in the morning. If I think of other reasons, I’ll email them to you later.

5. What pressure to use for each beer?

I’ve added beer style carbonation guide with a carbonation chart, I found via the Glacier Tanks website. You can read the chart to know how much CO2 pressure (PSI) you need at typical temperatures for beer.

Please note: The chart refers to the pressure you need, where beer is at equilibrium. Where the tank is at the correct pressure and you no longer need to add gas. I hope this makes sense! 

Again, I stress if you can achieve the desired CO2 level for your beer in the tanks. Then you don’t need to add sugar and go through secondary fermentation.

6. Filling into corny kegs

If possible, it’s best to fill into kegs under CO2 pressure. I think this is achievable (although, my knowledge of corny kegs is old – I’ve not used them in a long, long time). If you add a fitting to the CO2 inlet/outlet of the corny keg with a valve so you can let pressure out.

You can the purge the corny keg, before fill. Fill it with some CO2, then let the CO2 out (repeat a few times). Then as you fill the keg, slowly let the CO2 out, it will be displaced during beer fill.

Corny Kegs
These are corny kegs

It’s good for your beer when it comes to bottling from keg, you’ll get better results. As you’ll see less CO2 loss from beer breaking out, on filling kegs.

Adding more CO2 for bottling

I guess in theory if you’ve time; you can keg off what you need for draft. Then what you plan to bottle; add more CO2 into the head space, chill down the beer to 1C and carbonate till you achieve CO2 levels you’d like for bottling.

Then keg and bottle from them after, as is your normal process. If you’ve the time, and want to bottle at significantly higher CO2 content than for your draft beer.

Although, in this instance, is there are reason you don’t bottle straight from the tank? I think that’s it for now Norman, I hope this makes sense. It’s often hard to articulate technical aspects of brewing in written form.

Carbonating Beer in Small Breweries – Norman’s Reply & My Replies in Blue

Hi Neil, I’ve sent you pictures of my FV’s on WhatsApp. (I’ve shared them below)

Ok I see them. You don’t have a CO2 arm/CIP arm, from the pics I’m seeing. How do you clean the CIP clean the FV’s?

Please confirm, here’s the setup for from pilot tank below along with a typical unitank setup seen in most breweries.

Carbonating Beer in Small Breweries - Pilot FV Setup
My Pilot FV Setup – Sorry Not A Great Pic
Buying A Commercial Fermenter Tips
Diagram of a typical FV design

New Note: Norman sent me some additional photos later showing there is a spray-ball attachment at the back coming off what look like an RJT fitting. Please see the first pic.

There might be a way to to change the set up with some extra valves, stainless parts and a T-piece. It’ll cost a bit in stainless to do but well worth the investment in my opinion.

Carbonating Beer in Small Breweries - Set Up to Spund Beer

Please see the above diagram of the set-up I think will work best for you as you’ve only one 1-inch port to use for the PRV AND spunding.

Please note: The PRV valve should be connected directly to the tank, so it can’t be accidently closed off.

More pictures to come

This setup goes where the current PRV valve is connected to the tank with a tri-clamp. Please see the red circle for where I mean.

I’ve placed a butterfly valve after the PRV valve so, you can take off the fittings if needed and still keep the pressure in the tank but still be safe. As the PRV valve is still in situ.

Carbonating Beer in Small Breweries - Where the New Fitting Will Go

Carbonating Beer in Small Breweries – Noman’s Dry-hopping Technique

I have 2 blond ales, one of which is an IPA and I dry hop these. The hops go in in a net bag. So, are not loose. They go in after Primary (when it’s reached the target gravity), at the same time as the finings and syrup, with the beer chilled down to 3°C.

You can spund these beer until after you’ve added the dry-hops. It’s up to you; some people don’t like to add pressure until the dry-hop finishes (usually 4-days) and the hops dumped.

As these brewers say dry-hoping under pressure, mutes hop aroma. Some brewers will add pressure as soon as the hops are in. If you choose this option, then you can keep the pressure at 15PSI to start with.

Note: 15 PSI (pound per square inch) is the maximum working pressure of Norman’s tanks.

Or after adding the hops, just close off the CO2 out and let it spund. If there is any fermentation action, it means you maybe seeing dry-hop creep. When close to desired carbonation level use the chart from the first email, to set the right pressure for desired carbonation. 

Beers which aren’t dry-hopped can be spunded as soon as the fermentation has started (refer to original email). I begin spunding when the beer has dropped two Plato points.

Carbonating Beer in Small Breweries – Norman’s Other Beers

The other 3 beers (2 bitter beers and a Porter) are not dry hopped. I use Nottingham ale yeast and primary is usually done in 3 days in most conditions. Secondary fermentation is usually takes about a week to ten days.

Unfortunately, I don’t know what pressure that its sitting at. So need to get pressure gauges for my tanks. The beer is then chilled down again to 3c for kegging/bottling. I have also sent you some pictures of my kegs and bottling machine.

Topping up the pressure will be a similar time frame (or less) then you’re secondary fermentation. So, the spunding solution is viable.

Carbonating Beer in Small Breweries – Norman’s Tank Capacity

The tanks have a capacity of 400L, but I’m generally brewing in 200-300L batches, mainly due to storage capacity for kegs and bottles. Therefore, I suppose there is a lot of head space. I can obviously rectify that if you think that would be better.

More head space will actually help carbonate quicker. More CO2 to be absorbed. Most brewers do like to fill their FV’s to about 20% head space. More volume in tanks with less headspace, makes for cheaper being made beer.

Less man power for more beer. If you find some krausen comes out of the tank (if you’re not spunding). You can use an anti-foam agents like Batfoam (by AEB).

Carbonating Beer in Small Breweries – Maximum Working Pressure of Norman’s Tanks

I believe the maximum working pressure of the tanks is 15 PSI (pound per square inch). Generally speaking, I have a figure of 2.3 volumes for each beer, but I’m not sure I’m achieving that.

To achieve that, I’m using the syrup for secondary, but I’m interested in your comment about maybe not needing that. I’m using straight forward table sugar dissolved in boiling water and then chilled before adding.

I use Super F finings at this point, but also use carrageenan in the boil when brewing.

Yeah, spunding or topping up head pressure works. It’s how I carbonate all my beers, even the ones I dry hop. My tanks currently have a 15 PSI working pressure too. I’ve been brewing like this for years.

Furthermore, you can buy simple CO2 measuring/testing devices. The most well-known one is by Zahm and Nagel. There are cheaper versions out there. Many brewers in China use a Zahm and Nagel copy made here and it works well.

Basic CO2 Tester

Re filling the kegs from the uni tank – Norman’s Procedure

I’m going to have to find fittings that will enable 3/8 connections. The fermenters have 1″ RJT fitting on the racking arm, 1.5″ RJT at the bottom of the cone and 1″ triclamps on the sampling port and PRV. I’ve not seen anything like that.

OK you can work with that. I’ll send pics of my set up and manual kegging too. Note to self: need to do this after Christmas

Please Provide Some Pics and Videos

Do you have any pictures of gas connections for fv’s? I think the running off to keg and then adding more co2 and leaving for a bit before bottling is appealing. So basically I need to set up my fav’s a bit differently. 

Here is my simple gas connection setup:

Carbonating Beer in Small Breweries - CO2 Connection
Gas Connection Setup

Carbonating Beer in Small Breweries – Conclusions

Hey thanks for reading this post. As I say where possible I like to help people if I can, I was travelling on a train so, had some time to think out this problem for Norman. Also, it was a great question and the answers I thought could help others.

So, I’d like to thank Norman for allowing me to share the conversation we had. The conversation is still ongoing and will add to this post, if more interesting and actionable content comes up.

If you’ve any feedback or follow-up questions then please feel free to comment below or message me directly.

Likewise; if you need help with:
  • A new brewery project
  • Putting an equipment list together
  • Sourcing brewing equipment
  • Recipe formulation
  • Brewery procedure of processing

Please feel free to email me at:

Or add me to your preferred network by scanning one of the QR codes below and messaging me directly. Use my 25-years of brewing experience and installation knowledge to allow me to help you.

Related articles for suggested follow-up reading:

Hyper-local Brewing – Small-Scale Brewing Can Be Profitable: Hyper Local Brewing – Small Can Be Profitable – Asian Beer Network

Small-Space Brewing – How to Fit a Brewery In Tight Space: Commercial Small Space Brewing – Asian Beer Network

What Gets Missed When Buying a Brewery – Lesson I’ve Learnt: What Gets Missed Buying a Brewery? – Asian Beer Network

Skid-Mounted Breweries – The Pros and Cons: Small Affordable Skid-Mounted Brewhouse – Asian Beer Network

Neil Playfoot

Neil is a brewer with 25 years international brewing experience. Based out of China (first came in 2010) he works as a brewing consultant helping brewers with their projects and brewing processes. To find out what services Neil can provide your brewery please click here. If you'd like to contact Neil you can email at
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