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High Volume Brewing

You can brew 15 gallons (57 l) with a 10-gallon (38 l) brew system by taking a few different approaches. Longtime homebrewer Jester Goldman walks you through some ideas and weighs pros and cons.

Jester Goldman December 16, 2016

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Stepping up from 5-gallon (19 l) batches to brewing 10 gallons (38 l) at a time is fairly manageable, but what about bulking up further? There are plenty of 15-gallon (57 l) fermentors out there, from home-grown plastic malt extract drums to sweet stainless-steel conical tanks, and numerous options in between. You can even go larger if you’re game. The thought of brewing 15 gallons (57 l) at a time is awfully tempting, but before you commit, there are an ideological issue and a few logistical issues to consider.

The obvious question is whether high-volume brewing fits your brew style. If you’re the happiest experimenting with something new every time, larger batches will slow you down. The same is true if you’re a fickle drinker who would get bored with too much of the same beer. On the other hand, if you’ve settled on a dependable set of recipes, it might be nice to keep your taps well provisioned. Or perhaps you have a special event coming up and need a larger batch for it.

The weight of 15 gallons (19 l) fermenting is one logistical concern. Carboys and brew buckets work so well because, for most of us, 5 gallons (19 l) is easy enough to lift and move around. A 15-gallon (57 l) fermentor is more or less staying in one place. Still, if you go with a conical fermentor, you won’t need to worry about racking; you can just drain off the trub and other sediment.

The real challenge is filling up that 15-gallon (57 l) fermentor. You can either scale up the rest of your home brewery to handle 15-gallon (57 l) batches, combine multiple smaller batches, or brew a high-gravity wort and dilute it. Each approach has its pros and cons.

Bigger Brewing

Upgrading the rest of your equipment to handle the larger batch size is a simple, but pricey, solution. You’ll need larger pots for hot liquor and boiling, as well as a mash tun that can handle at least 30−35 pounds (13.6−15.9 kg) of grain. You’ll also want a pump (unless you’re using a tiered gravity system) if you don’t already have one; it’s the most efficient way of moving the wort around.

Money doesn’t solve everything, though. You’ll have to adapt your process, too, especially if you’re used to 5-gallon (19 l) batches. Three times the water and grain in a mash means a lot more weight and the inertia of that much thermal mass. Temperature changes will take more time, so you’ll need to be tighter on hitting your dough-in target, and step mashes may be a bit of a challenge. Stirring that big a mash can also be hard but very important because it’s easy to miss dry bubbles of grain in the larger volume. Also, when you scale up your mash tun, the geometry may be an issue. Too deep a grain bed can lead to compaction and stuck sparges. It can even over-stress a false bottom and collapse it.

Thermal inertia cuts both ways, too. Heating the mash or starting a boil requires more patience, but you’ll also need to be fairly vigilant about boil-overs because they can quickly get out of hand. None of this is impossible, but your first few batches will be a learning experience.

Splitting Up

A cheaper alternative is to brew two or three separate batches and combine them in the fermentor. This has the advantage of getting by with most of your current equipment, but it does take more time and effort. If you go this route, you’ll need to decide how to break things up. Will you brew each portion as a standalone beer or will you scale up to a single larger mash, but split the boil steps?

Standalone beers are simpler, but much more time consuming. You either brew them in series, which makes for a long brew day, or you can try to interleave the steps, such as starting your next sparge while the previous batch is starting to boil. Be warned that parallel brewing demands a lot more attention, and you may want to have extra burners on hand to cut down on resource contention. Otherwise, you’ll be spending a lot more time heating your mash water (even if you preheat it) and wort. Of course, you could also stretch out the brewing across a couple of days, letting the first portion start fermenting and adding the next sub-batch later.

A single massive mash with split boil steps offers the same issues of scaling up: you’ll need a bigger mash tun that can handle the extra volume and weight, and the larger thermal mass will impact your process. There are also a couple of less-obvious concerns. The first is that you’ll need to account for the gravity difference over the course of your sparge. First runnings are quite a bit bigger than the tail end of the sparge, so you may want to mix the wort before splitting up the boil. Ignoring this will affect your hops extraction efficiency, plus it’s harder to calculate the actual OG until everything’s blended, making it harder to brew repeatable beers. The second concern is wort spoilage. If you can’t boil the portions in parallel, the later batch can be a target for bacteria while waiting its turn on the burner.

Larger Mash

Another possibility is to do a larger, single mash, collecting a smaller volume of high gravity wort to be diluted in the fermentor: 10 gallons (38 l) of 1.085 wort plus 5 gallons (19 l) of water settles out to 1.056. It’s a workable approach, but the larger mash is harder to handle and your process will be inherently less efficient than the other two approaches. Mash efficiency will likely be lower because there’s less water to rinse all the sugars out. You’ll need extra hops, too, because higher gravity boils adversely affect hops utilization. Fortunately, there are tables that can help you figure out the impact.

Chart Your Course

All things considered, the full system upgrade is probably best, but if you’re on a budget (or are brewing for a one-time event), then blending separate batches in the fermentor is a close second. If you’ve made the leap, share your experience in the comments.

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