Closed-Transfer System

Modifying a fermenter lid

A closed-system transfer from fermonster fermenter into a Corny keg.
Photos courtesy of Dom Gallo

As a homebrewer, my goal has always been quite straightforward: Make beers better than the ones I can buy. Though far easier said than done, this goal has always resonated with my competitive nature and desire to place my best efforts in all that I do. It has influenced me to research and learn as much as I can about this beautiful hobby and has motivated me to continuously improve from one batch to the next. This journey has led to concepts and practices that have changed my brewing forever: Fermentation control, water chemistry, and what I consider the most crucial for beer quality, the ability to minimize/eliminate oxygen contact post-fermentation.

When I started looking at ways to achieve that final concept, I decided it was time to upgrade my equipment to be able to put this practice into place. I quickly realized that stainless steel equipment with closed transfer capabilities was out of my comfortable price range and their PET counterparts were not much different than the PET FerMonster that I already owned. The big difference was the fact that they had liquid and gas connections for transfers. It was at that moment that I realized with a drill bit and a few parts I could convert my FerMonster to do the same thing. It didn’t take long to put this idea to use.The next day, the modified FerMonster lid with closed transfer capabilities was born.

For this DIY project you are simply drilling a solid FerMonster (or similar large-mouth PET carboy) lid and fitting it with gas and liquid ball-lock posts. Then you are installing a floating dip tube (I recommend the one offered by Brew Products called the Clear Beer Draft System, to the liquid bulkhead. This essentially turns the fermenter into a modified bright tank with a low pressure rating. 

This build essentially turns the fermenter into a modified bright tank with a low pressure rating.

With this lid you are able to perform the following tasks that had eluded me before: Connect your fermenter to your gas supply during cold crashing, prevent oxygen contact during dry hopping, dry hop with positive pressure, use fermentation gas to fully purge serving kegs, and transfer from your fermenter to your serving kegs without worrying about your beer oxidizing. 

When all of these minor tweaks are made to your beer, it will help you to maintain that hops-straight-out-of-the-bag character in hoppy beers, bold and complex profiles in malt-forward styles, and subtle nuances in your light ales and lagers.

The only real caveat with using this system is the possibility of having your regulator set too high. Just be sure to check before use each time. Most PET carboys are rated to 15 psi, but I don’t go above 5 psi.

Tools and Materials

  • FerMonster carboy with solid lid
  • FerMonster carboy replacement lid o-ring
  • Ball-lock post bulkhead — gas-in 
  • Ball-lock post bulkhead — bev-out 
  • ¼-in. barb x ¼-in. female threaded stainless barb
  • 5⁄8-in. O.D. x 7⁄16-in. I.D. x 3⁄32-in. o-ring
  • Floating dip tube 
  • ½-in. (13-mm) spade tipped drill bit (3-in./7.5-cm or longer)
  • (2) Grooved joint pliers
  • FerMonster lid opener