Author: Henry Chen Publish Time: 2026-05-06 Origin: Jinan Cassman Machinery Co., Ltd.
Choosing the right fermenters might be the most important equipment decision you'll make for your brewery. Your fermenters are where the magic happens—where yeast transforms wort into beer. Get this choice right, and you're setting yourself up for consistent, quality production. Get it wrong, and you'll be fighting your equipment instead of making great beer.
We've spent years helping breweries spec out their fermentation systems, and we're going to share everything we've learned. Let's walk through the key decisions you need to make.
The first question we always get is "what size fermenter do I need?" The answer isn't simple because it depends on several factors:
Your target weekly or monthly production volume
Your batch size and brewing frequency
Space available in your brewery
The turnaround time between batches
Whether you're doing simultaneous fermentation of different styles
A common starting point for many craft breweries is having enough fermenter capacity to hold 1-2 weeks of production. So if you're brewing 10 barrels per week with 5-barrel batches, you'd want 2-3 fermenters minimum.
Your fermenter should comfortably hold your batch size with room for fermentation activity. We generally recommend that your fermenter capacity be at least 20-30% larger than your batch size. This gives you:
Space for vigorous fermentation foam (especially important with healthy yeast)
Ability to do closed transfers without overflow
Flexibility for hop additions or dry hopping during fermentation
Going too large isn't ideal either. A half-full fermenter can lead to oxidation issues and inconsistent fermentation because the headspace contains too much oxygen that needs to be purged.
Here's something many new brewers overlook: conical fermenters make harvesting yeast easy. The cone shape at the bottom allows you to collect yeast from completed fermentations and repitch into your next batch. This only works well if you're not trying to harvest from a vessel that's nearly empty.
If you're running any kind of serious production, stainless steel is almost certainly your answer. The reasons are straightforward:
Durability: A quality stainless fermenter will last decades with proper care. We're still seeing 20-year-old units in operation regularly.
Cleanability: Stainless steel has a smooth, non-porous surface that doesn't harbor bacteria or impart flavors. The ability to clean and sanitize thoroughly is non-negotiable for food-grade production.
Thermal conductivity: While not as conductive as copper, stainless steel does allow for jacket cooling that gives you control over fermentation temperature.
Professional appearance: Let's be honest—in a taproom setting, your fermenters are visible. Polished stainless looks professional and impressive.
This is where jacket design becomes crucial. Your fermenter needs to maintain proper fermentation temperatures, especially for ales (which typically ferment at 64-72°F) and lagers (which need 45-55°F).
Look for fermenters with efficient cooling jacket designs. Multiple jackets (often on the cone and lower body) provide better temperature control than single-jacket designs. Some premium units even have glycol cooling built into jackets for precise temperature management.
Plastic (conical) fermenters: These exist in the home brewing world and some small commercial applications. We generally don't recommend them for anything beyond very small craft production. They scratch, they stain, and they can harbor bacteria in micro-scratches that become impossible to clean.
Glass carboys: Again, primarily home brewing territory. Great for small batches but impractical for commercial volumes due to weight, fragility, and limited temperature control options.
Not all fermenters are created equal, even among stainless steel units. Here's what to look for:
The cone at the bottom of your fermenter needs a way to empty. Most commercial units use a bottom dump valve system. This should be:
A true 2-inch or larger dump valve for fast emptying
Easy to clean and sanitize
Configurable to your existing valve standards
Avoid units with small, hard-to-clean dump systems. Trust us—you'll curse those decision when you're trying to empty a full fermenter quickly.
Open fermentation is traditional and used by some craft breweries, especially for certain beer styles. It requires less specialized equipment.
Pressure-capable fermenters allow you to ferment under pressure, which is essential if you want to:
Carbonate during fermentation
Do closed transfers
Reduce off-flavors from oxygen exposure
Handle high-gravity beers
For most modern craft breweries, we recommend pressure-capable units. The flexibility is worth the extra cost.
You need ways to:
Take samples for gravity readings and tasting
Measure temperature accurately
Add ingredients during fermentation
Inspect the interior
Quality sample valves, thermowells, and access ports make your life much easier. These should be standard on commercial units, but check carefully.
Look for features that make fermentation smoother:
Interior polish: A 2B finish or better is standard for commercial units and makes cleaning easier
Legs or stands: Make sure they're adjustable for leveling on uneven floors
Moveable options: Some units come with casters for flexibility in your brewery layout
Insulation jackets: These help maintain temperature and reduce glycol costs
Let's walk through a practical example. Say you're planning a 5-barrel brewery with these goals:
Brewing 3-4 batches per week
Primary fermentation taking 10-14 days
Some batches potentially held longer for aging
Flexibility for different styles simultaneously
For this scenario, we'd typically recommend 4-6 fermenters minimum. Here's why:
If you brew twice per week with 5-barrel batches, you're producing about 10 barrels weekly
At 14-day primary fermentation, you need capacity for 20 barrels minimum (two weeks of production)
With some flexibility for aging or simultaneous styles, 4-6 vessels gives you breathing room
Add a few bright tanks for carbonation and conditioning, and you have a functional fermentation cellaring strategy.
New breweries often skimp on fermenter count, thinking they can turn tanks faster than realistic. Fermentation takes time. Plan for delays, adjustments, and styles that need longer contact.
If you're buying cooling-jacketed fermenters, you need a glycol chilling system. Don't buy the fermenters without planning how they'll actually be cooled. Undersized glycol systems lead to temperature control problems.
The cheapest fermenter might save you money upfront but cost you in features that make daily operation practical. Sample ports, proper valves, and good temperature control aren't luxuries—they're essentials.
We strongly recommend thinking about where you want to be in 3-5 years when making equipment decisions. Buying fermenters that you can expand into is almost always smarter than buying the minimum and replacing later.
When you're evaluating fermenter options, we suggest creating a spreadsheet that weighs:
Initial cost per barrel of capacity
Quality of construction and materials
Temperature control capability
Features included vs. add-on costs
Warranty and support reputation
Lead times (some manufacturers have very long waits)
At Cassman, we build fermenters to last and help you think through these decisions. We know that the right fermenter setup depends entirely on your specific situation, goals, and production plan.
Henry Chen, CEO
Getting your fermentation right is foundational to everything else in your brewery. Take the time to think through these decisions carefully. If you're wrestling with any of these choices, we're happy to talk through your situation and help you find the right configuration.
