Build a better blowoff assembly

Most seem to only offer a thermowell or blowoff tube. How about both!

Posted by Ben Griffith on 2016-12-21

The Reason

I got my first stainless conical about 2 years ago. It is a Blichmann 14 gallon Fermenator. I was in heaven. All the shiny stainless and tri-clamp fittings. It was great, and it still is. Except one small problem: the 1.5" hole in the top of the conical made for a bung and an airlock. Now in some cases, an airlock will work just fine. However, from my experiences, 9 out of 10 times I am going to need a blowoff tube.

The Dilemma

The only solution, and similar solutions for other conical brands, was to buy an expensive assembly that performed one function. In particular to the Blichmann conical, the assembly runs for about $120-130 depending on where you shop.

Blichmann Blowoff Assembly

Now this isn’t saying it’s a bad product. This will last forever given the proper care and would perform exceptionally. However, the flaw is, where do I put my temperature control probe?

Temperature Control

One of the biggest improvements with fermentation is controlling the temperature. Having your probe on the outside of your fermentation vessel doesn’t accurately portray whats going on inside. Fermentation is a chemical reaction. This reaction produces a small amount of heat which can raise the temperature internally compared to the outside of the vessel. There is also the case of the mass of fluid and the temperature differential between the outside edge and the center of the vessel. The best way to determine the core temperature of your fermentation is with a thermowell. So how do we incorporate a thermowell and a blowoff assembly with only one port?

Part List


The first step we need to do is put together the three main parts: thermowell, tri-clamp adapter and barb.

1/2" NPT 12" Thermowell Tri-Clamp to 1/2" NPT Tee 5/8" with 1/2" NPT Hose Barb

Assembly is straight forward. You will want to thread the thermowell into the top of the tee, and the barb on the side. This is the only way this configuration will work so it’s pretty fail proof! Don’t forget to add thread tape to all of your NPT connections.

Thermowell Added Barb Added

Next, if using a Blichmann Conical, you need to attach the Bottom Dump fitting. This is the same fitting used if you purchased their blowoff assembly and fits the pre-cut hole in the top of the conical.

Top of Bulkhead Bottom of Bulkhead

Now it should be very apparent how this is going to work. The thermowell will penetrate almost to the center of the vessel, while still leaving space within the NPT Tee for Co2 and yeast to blow out. The extra large 5/8" Barb helps to ensure we don’t get any clogs. Most 1/2" barbs inner diameter are a little smaller. Using a more flexible 1/2" ID silicon tube will go onto this barb fairly easily and end up in a blowoff bucket.

Thermowell/Blowoff Underside

Now that it’s put together, all we need to do it attach it to our Tri-Clamp bulkhead on the lid of our conical using our gasket and sanitary clamp.

    Mounted to the bulkhead And Done!

Pushing with Pressure

Another advantage to this setup is being able to swap the barb out with any 1/2" NPT fitting. When I am ready to cold crash, I can take the barb off and put a smaller one on. Then, I can hook up my Co2 tank and add a small amount of pressure to it. As the beer compresses due to the cold, I will be sure to keep a positive Co2 pressure within the vessel.

Later, when I am ready to keg, I can apply more pressure to the vessel to force it into a keg. This keeps a layer of Co2 present within the vessel and keeping oxygen out.