Introduction: Keg-onical Simple Stainless Steel Spunding Controlled Fermenter

  • So, you want the ease and convenience of a stainless fermenter, the ability to remove your yeast cake without messy transfers to secondary, you want to be a to save on gas, and time? You want to be able to do all of this without breaking the bank?

    This solution isn't the most ingenious out there. That's why I'm calling my keg-onical a dim tank rather than a bright one.

    It requires a minimum of parts and tools to put together.

    Required tools:
    Drill, and bits
    Flathead screwdriver #0
    9/16" wrench
  • 5/8" wrench
  • Hack saw
  • Files and sandpaper
  • Soldering torch
  • Ball peen hammer

  • Parts required:
    1@ keg - make sure yours is legally obtained.
    2@ 1/2" copper sweat tee
    2@ 1/2" female sweat x 1/4" FIP
    1@ 2" copper sweat end cap
  • 1@ 2" tri clamp
  • 1@ 1/4" 0-30PSI gauge
  • CR25-100 PRV
    2" Tri clamp and gasket

    This came to maybe $50 in parts though I had most of them laying around already

Step 1: Remove the Spear and Clean Your Keg

*it is important that you release pressure from your keg before you go any further.* Not doing so may cause serious injury. Not doing so *Will* cause you to be soaked in the beer residue left in the keg.

If you have removed a spear before you'll know how to do this. If not it's pretty simple.

First - ensure that you have released the pressure on your keg. if you don't do so you could be injured, and will certainly be covered in old gross stale beer.

Simply use your screwdriver and pliers to remove the retention ring. take your screwdriver and pry out on the ring, then grab on with your needle nose pliers to remove the ring. Then rotate the tabs to line up with the cut outs. Remove the spear and set it aside. try not to damage or bend these parts in the process. if you have a keg washer you will want to re attach the spear so as to wash your fermenter in between batches.

If you have a keg washer - or might build one in the future you'll want these parts for later.

dump any excess liquid. wash and (before use) sanitise.

Step 2: Build the Base for Your Spunding Cap

if you have thick sheet copper you could just cut disks out of it. I have one that I build by buying a 2" Tri Clamp end cap, and drilling and tapping holes in it. but tapping SS is a royal pain without a proper machine shop. so I'm doing it with solder this time instead.

I bought a 2" copper end cap. then cut it about 1/4" from the flat end to remove excess. then I hit it with the torch to soften it. copper work hardens so if you haven't had much practise with your ball peen hammer before this you might need to do this more than once.

you can tell that you've heated it enough when you start seeing colour changes in the metal.

once you have a nice flat disk you can proceed on to the next step

Step 3: Make Your Saddles

this step is very similar to the previous one. you might want to do them concurrently.

cut your 1/2" tee's in half lengthwise. after that you'll need to heat treat your copper again in order to soften it. you want to do this to both pieces of each.

once you have them softened, take some little bits of scrap copper and insert it in the joint of the tee. this will help it from deforming while you flatten it out. I used the vice grips to star it off, and then finished with the hammer. do whatever works for you.

once that's don't flatten out the back sides of the tees. you'll cut these down finish filling out the top of the disk we made in the previous step.

sand and flux everything.

Step 4: Solder It All Together.

I did most of my heating from below. I set this up on a couple of bolts held in the bench vise. as I said before make sure you have lots of flux on there. I used a tonne of solder too, to be honest. not that much risk in using too much. it'll just drip off at the point that you put too much in. but the surfaces aren't perfectly flat and so there are some gaps. I let the extra solder fill all of that.

after this you need to drill holes for air access. I came down through the threading from above because that way I know they are centered. 3/8 filled the space fairly well and was easily accessible to me, but you could go bigger or smaller if you wanted, so long as there isn't a significant restriction it'll operate the same.

you also need to clean the fux off of the surfaces now. I left mine sit in a vinegar solution over night, and then ran it through the dishwasher.

Step 5: Bolt It All Together

The assembly of the spunding cap is pretty self explanatory.

pick one of the two trunks to mount the pressure gauge on. you need to mount the gauge first because its wide enough to block access to the other fitting. make use to apply your Teflon tape first to ensure you get a good seal. a spunding valve that leaks is no good. then thread in your PRV into the other. if you have previously used this somewhere else, or disassembled for some reason you will need to apply tape there as well. they come with a sealant already on the surface of the threads.

Step 6: Transferring

At this point you have a fermentation ready chamber.

I use a sanke system in my kegerator, so this is the logical progression. I have the sanke flange that we cut of an unneeded keg that was trimmed off enough that there is just enough of a lip that it will clamp onto the flange of the fermenter with a tri-clamp. The spear was reassembled on this. when I do my pressurised transfer out of the fermenter I use this. (just make sure to bleed off the pressure in the tank before your remove your spunding cap as it could be dangerous) liquid out on the fermenters coupler goes to liquid out (without check valves) on a second coupler. that coupler is attached to the serving keg. I fill two serving kegs from the one fermenter, and then I left the almost empty keg, and rinse out the yeast.

if you want to work with corny kegs, you could go back to steps 3&4 and basically build another cap, but with ball or pin lock ports on top (and a dip tube) if someone does this can you take some pics of the process and let me know if you have any issues. i'll post it in here as well.

Step 7: Conclusion

your new fermenter should be versatile. dry hopping or the addition of late stage adjuncts is as easy as popping open the lid and dropping them in.

the spunding system replaces the need for an airlock, and the risk of them running dry or getting knocked off. I find this is especially helpful when I brew a mead and want to allow it to condition for months at a time

while this isn't the perfect system it sure beats spending a thousand dollars on a system that will give you very similar results. I estimate that most home brewers could have this put together for less than $100 even if they have to pay for the keg. That's pretty significant when you compare to some of the commercially available SS Fermenters, even at the 20-50L sizes