Author: Marshall Schott

When healthy yeast is is pitched into sugary wort, fermentation is going to happen regardless of what container it’s in. For homebrewers just starting, this is often a plastic bucket or glass carboy that, while cheap, lack many conveniences that simplify the process of racking out of said vessel. Still, they work.

As the hobby of brewing at home has grown, so too have the options for fermentation vessels, as well as our understanding of how certain variables affect the beer we’re making. Let’s face it, homebrewed beer doesn’t have the greatest reputation, and it’s likely certain issues that occur during the fermentation process or packaging, such as oxygen exposure, have contributed to this perspective. Because of this, manufacturers have developed unique vessels that allow homebrewers to employ many of the same processes used by commercial brewers, which is exactly what Spike Brewing intends with their new FLEX+ fermenter.

When the folks from Spike Brewing reached out asking if I’d like to review a new fermentation vessel, I was admittedly a bit hesitant, as I couldn’t really imagine how it would improve upon what I was already using. It was only when they shared a list of features with me that I realized the FLEX+ could be a game-changer, so I agreed to put it through the paces and share my thoughts.

The product reviewed for this article was provided by the manufacturer in exchange for an honest review; no other compensation was provided. The opinions expressed in the article are solely those of the author and a concerted effort was made to approach the review from an unbiased perspective.

Assembly

I received a FLEX+ prior to Spike publicly announcing it, as I wanted to have time to use it for a few batches before penning a review. It arrived nicely packaged a few days later.

My first thought when unboxing the unit– what the hell have I gotten myself in to? So many parts for such a relatively small fermenter.

With some prior tri-clamp (TC) experience, I soon realized it really wasn’t as bad it looked and began assembling the unit.

In earlier conversations with Spike, I’d mentioned to them what I found most appealing about the FLEX+ is the ability to ferment and cold-crash under pressure, as well as perform oxygen-free transfers, so they included a few accessories to make this possible.

With everything put together, I ran a couple tests with water and external CO2 to ensure no leaks before proceeding with cleaning and passivating the FLEX+. As this point, it was ready to use.

Detailed Feature Overview

Spike Brewing has developed a reputation for providing brewers with stainless gear with high quality sanitary welds, and the FLEX+ certainly was no exception. The steel had no visible imperfections and the welds were all seamless.

Tri-Clamp Fittings

Every fitting that connects to the FLEX+ does so via tri-clamp, which is awesome because they’re incredibly easy to remove and clean, which means reduced risk of contamination.

Some may view this as overkill on the homebrew scale, but having used most types of fittings in my brewery, I’m a believer. There’s a reason professionals rely on tri-clamp fittings.

High Pressure Lid

The high pressure lid gets attached to the vessel body with a large v-band clamp, which when tightly secured, allows the FLEX+ to hold up to 15 psi of pressure.

For the most part, fermenter lids aren’t really anything special, usually containing a hole for the airlock stopper and a simple way to secure it to the vessel. This is not the case for the FLEX+, which comes with a domed lid with various rad features.

Modular Viewing Port

One of the more unique features of the FLEX+ is the 4″ modular TC port at the top that, with the included clear plastic cap in place, allows one to observe the beer during fermentation. This port also comes in handy when making dry hop, gelatin, or any other additions.

I’ve found the beer can be slightly difficult to see through this port, especially since I ferment in an enclosed chamber, an issue easily resolved with my phone’s flashlight.

Blowoff Port

Next to the viewing port is a 1.5″ welded ferrule where an included TC barb fitting gets placed. Attache a piece of blowoff tubing, throw the other end in some water, and bam, there’s your airlock.

This port is also where an add-on gas manifold can be attached that makes fermenting and transferring under pressure possible. The manifold comes with a pressure gauge, 15 psi PRV, and ball lock gas post.

More on this in a bit…

Internal Volume Markings

Etched onto the inside wall of the FLEX+ are volume markings that make racking accurate amounts of wort, juice, or must a breeze.

Stainless Handles with Soft Cover

The handles on the FLEX+ are nice in that the area one grabs is covered with a fairly soft plastic material that makes picking the unit up much more comfortable.

What’s really weird, though, is the warning etched near the handles.

Do not lift when full? Isn’t that what handles are for? Lifting? How else am I get my wort-filled vessel into my chamber? I like to live life on the edge and have relied on these handles to lift my filled FLEX+ every time I’ve used it, no tragedy has struck… yet. Proceed at your own risk, I guess.

Mid-Level Multipurpose Port

A little over halfway down the FLEX+ is a 1.5″ TC port that comes with a stainless cap.

There are various accessories that can be used with this port such as sanitary sampling valve or a thermowell for precise fermentation temperature control.

Bottom Racking Port with Butterfly Valve

Toward the bottom of the FLEX+ is another 1.5″ port where the racking arm and butterfly valve get attached.

I’d never used a butterfly valve before and initially thought it was cumbersome feature likely intended make the homebrewer feel more like a pro. But after using it multiple times, I’ve had a change of heart. Not only does it make transfers really simple, but it’s completely sanitary and super easy to clean.

Between the valve and the fermenter is a racking arm with an OD that’s quite a bit larger than most others I’ve used, which means less risk of clogging.

Once installed, a small position indicator lets you know exactly where the racking is. Sounds like a non-issue, but it is incredibly convenient, particularly for those who dry hop loose.

Stick-On LCD Thermometer

Cheap but surprisingly effective, Spike includes a stick-on thermometer with each FLEX+, making it easy to read the fermentation temperature.

I keep the probe from my temperature controller secured to the side of the FLEX+ and it has reliably read within 1°F/0.5°C of the LCD thermometer.

Legs

The FLEX+ rests on 3 legs that are welded onto the unit with the same quality as all of the other ports.

Nothing too special here, just wanted to point out they can be adapted to fit add-on extensions that raise the fermenter up either 9″ or 18″.

How I Use The FLEX+ Fermenter

Using the FLEX+ is mostly self-explanatory, though its 15 psi rating means some seriously cool stuff can be done. While some of the methods I use can likely work with the included blowoff barb, the gas manifold makes it really easy.

After cleaning and sanitizing the vessel, I rack wort into it from my kettle then place it in my temperature controlled fermentation chamber. While the mid-level TC port could be used for a thermowell, I do what I’ve always done and tape the probe of my controller to the side of the FLEX+. Seeing as my groundwater tends to be fairly warm, I usually end up leaving the wort alone for a couple hours before returning to pitch the yeast, which I do through the 4″ top viewing port.

After reattaching the cover and making sure all other connections are tight, I connect a blowoff tube to the post on the gas manifold, the other end of which gets attached to the gas post on a keg I previously cleaned and fill with sanitizing solution. Next, I run a line from the liquid post of the sanitizer filled keg to the liquid post of a clean empty keg, thereby creating a simple CO2 capture device.

As the beer starts to ferment and the pressure created in the sealed FLEX+ rises, the sanitizing solution is pushed out of the first keg and into the empty keg, effectively purging the first keg of oxygen. This all happens pretty quickly, within the first 8 hours in my experience, after which the second keg acts like a typical blowoff vessel.

My love of this method is ineffable.

Once fermentation activity begins to wind down, I disconnect all of the lines and allow the beer to finish attenuating under a little pressure, knowing the PRV won’t allow it to build up any higher than 15 psi. I then use this pressure to collect oxygen-free hydrometer samples using a sanitized TC barb fitting attached to the sanitized butterfly valve. I’ve found 5 to 8 psi will clear the diptube of any debris and result in a hard enough pour to knock most carbonation out of solution. When FG is reached, I proceed with cold crashing by reducing the temperature of the chamber to 33°F/0.5°C. If the gauge is still indicating 5 psi or higher, as is often the case, I’ll leave it alone, otherwise I’ll connect external gas at 1-3 psi.

Of the batches I’ve fermented in the FLEX+, I’ve only fined one with gelatin, which is an obvious vector for oxygen exposure. To combat this, added the gelatin as quickly as possible through a small crack in viewing port with the gas from my tank still flowing; then I purged the vessel 3 times once sealed. Imperfect, but better than doing nothing at all.

After a day or 2 of cold crashing, I move on to packaging, which is another area the FLEX+ shines, as it allows me to rack the beer to a keg without moving the vessel out of my chamber. After sanitizing everything that will be in contact with the beer, I attached the TC to flare fitting included with Spike’s closed pressure transfer kit to the butterfly valve then connect the transfer tubing to the flare.

At the other end of the transfer tubing is a liquid disconnect, which gets attached to the liquid post of the keg that was previously purged with homemade CO2. With approximately 3 psi of gas on the FLEX+ and a gas post depressor in place, I open the butterfly valve and let the beer flow.

I don’t make too many highly hopped beers, and even when I do dry hop, I use stainless mesh filters and drop them into the viewing port. I’ve not had any issues with clogs or trub transfer. If I did, a simple loosening of the butterfly valve TC allows the diptube to be easily repositioned above the trub line. Bubbles in the line indicate transfer is complete, at which point I disconnect it from the keg, turn the gas from the tank off, place the filled keg in my keezer, and get on with cleaning as usual.

| The Verdict |

Through both personal experience and the results of exBEERiments, I’ve come to view cold-side oxidation as being one of the main culprits of shitty beer, which has led to me employing numerous methods to reduce this risk, from skipping the cold crashing step to kegging with a CO2 filled balloon attached to my fermentation vessel. What I appreciate most about Spike’s FLEX+ is that it was clearly designed with this in mind, allowing one to use pretty much any standard cold-side method in an essentially oxygen-free way including cold crashing, hydrometer sample collection, and packaging.

With its ability to hold up to 15 psi of pressure, there are numerous other badass things the FLEX+ can be used for, such as purging a keg with naturally produced CO2, which has become a normal part of my process. The FLEX+ also makes pressurized fermentation a breeze, a killer feature for those who feel this is required for fermenting lagers warm, as well as carbonating directly in the fermenter.

In thinking of downsides of the FLEX+, other than the obvious it-cost-more-than-a-bucket, a few things do come to mind, the first of which is its size. Immediately upon assembling the FLEX+, I realized it had a noticeably larger footprint than other fermenters I’ve used, and sure enough, I could only fit one in my chamber. Not a huge deal for the majority of people who brew single 5 gallon/19 liter batches at a time, but a slight bummer for those of us who ferment two batches simultaneously. Another lacking feature that could be viewed as a con by some is that the FLEX+ has no trub dump, which would not only make collecting and reusing yeast easier, but it’d be a neat feature for those interested in carbonating and potentially serving from the same vessel.

There’s no denying Spike’s FLEX+ is a luxury piece of homebrewing gear at $375 with standard accessories, though it does offer many of the same conveniences as more expensive options. I care a lot about reducing cold-side oxidation in my beer, and seeing as I’m not getting any younger, lifting full fermenters in and out of my chamber is becoming a chore. I absolutely love that with the FLEX+ I can ferment, pull samples, cold crash, and package without risking oxygen exposure or moving the vessel. And the ability to purge kegs of oxygen using naturally produced CO2 further improves the packaging process while saving me money on gas refills. I’m a huge fan!

The Spike FLEX+ is currently available at Great Fermentations or direct from Spike Brewing. If you have any questions about this product, please don’t hesitate to leave them in the comments section below!

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