Fermenter Design with Blow Off Tube

Today we are going to talk about how to convert an HDPE bucket into a fermenter. For this, we have used a commonly available milk can. However, you can use any food-grade airtight vessel for this purpose. Do go through our fermenter checklist before purchasing one.

Fermenter Design with Blow Off Tube

Today we will convert a milk can or a simple kitchen utensil into a fermenter with blog off tube as an airlock.
Prep Time10 minutes
Active Time15 minutes
Total Time25 minutes
Keyword: bio-reactor, home made fermenter, milk can
Yield: 1 Fermenter
Cost: 500


  • milk can or a large airtight vessel
  • drilling machine
  • soldering iron


  • 1 m vinyl PVC pipe
  • 1 piece airlock
  • 1 set pipe fittings


  • Find a milk can or a large plastic vessel. Check the inner surface for scratches, rough surface or dead zone where microbes can hide.
    simple low cost fermenter
  • Find a 22mm pipe fitting that will fit your fermenter
    fermenter pipe fitting
  • Find the matching screw that can be attached to your fermenter lid
    matching fermenter screw
  • Use a slug buster to drill a perfectly round hole in your fermenter lid
    screw type hole driller
  • Attach the screw fittings to the fermenter lid and seal the whole setup.
    fermenter screw attachment
  • Now insert it to the lid and inspect the assembly for any leakages. You can use a food grade silicone or any other food grade sealant to fix the gaps.
    fermenter inspection
  • Now attach your blow off tube and your assembly is complete.
    fermenter design with blow off tube
  • Don't forget to santize your fermenter bio-reactor assemby with a brewing sanitizer. A rinse free sanitizer means that one does not need to wash off the residual chemical with water afterwords. It also removes all microbes and oil film where infection can hide.
    brewing sanitizer rinse free

Attaching airlock to fermenter

  • You can attach a S type airlock to your fermenter lid using a sleeve.
    Airlock attached with a sleeve
  • This contraption can now to attached to your fermenter lid.
    home fermenter with airlock

Attaching 3 Piece Airlock

  • If you are unable to get the screw that can be attached on the lid. Use a can use a cork with hole or a grommet as well
    grommet for airlocks
  • Here is how your fermenter will look
    3 piece airlock fermenter

Fermenter Cold Crashing

  • One of the drawbacks of the blow-off tube is temperature variation. When we cold crash or during cold winter nights, the drastic fall in temperature causing the air in the headspace to contract. This will cause the airlock in your fermenter to suck back oxygen and lead to oxidation of alcohol into vinegar.
    airlock seal during cold crashing
  • You can attach a simple plastic cap to seal it. If you are unable to find one use a faucet plug to seal the fermenter lid.
    beer tap cover faucet plug
  • Here is how your fermenter would look once you seal it for cold crashing
    fermenter sealed for cold crashing
  • Alternatively you can use a duotight or keezer fittings to make a blow off tube with a faucet. This can be turned off at night or during cold crashing to prevent sucking back of air during drastic temperature changes.
    blow off tube with duotight

Inserting Cork

  • You can also insert the cork with hole in your fermenter to attach the airlock


This fermenter is ideal for those who are trying to make a simple home brew fermenter. Remember any food-grade airtight vessel can be converted to a fermenter.

Buy Related Products

Don’t forget to inspect for scratches. Also go through the equipment checklist


milk can fermenter with blow off tube
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