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Plastic Carboy: Temperature Control

Every household has a plastic carboy lying around. They cost a mere 100 bucks (USD$1.2) and are used for RO drinking water. They are also used by many brewers to ferment wine and beer. Today we’re are going to talk about how to regulate its temperature.

Home Brew Fermenter temperature makes the difference between a clean crisp brew and a hangover. Summer and lockdown are ideal conditions for brewing, but temperature higher than 25 Degree Celsius is not good for fermentation. Glycol based industrial temperature controllers are very expensive. Here is a simple DIY fermenter that can help you save costs and still get the work done. We don’t recommend glass carboys because the glass is a thick insulator. Hence it is difficult to regulate fermentation temperature in it. If you are fermenting lagers We strongly recommend using a Corny Keg.

Recommended prior reading:

  1. Pros and Cons of Different Fermenter Designs
  2. Making DIY Carboy Fermenter
  3. Brewing in summers
Summer Fermenter with water cooling
4 from 3 votes

Temperature Control Carboy fermenter

Reduce hangover and off flavors by reducing the fermentation temperature in your plastic carboy. Step by Step guide to attach a simple Aquarium pump to make a recirculation chiller for your fermenter. Pump consumes 20W of power and fan (with regulator) consumes about 50W so total power consumption is 70W for a 10 degrees temperature drop and 1000/-INR investment in equipment.
Prep Time20 mins
Active Time10 mins
Total Time30 mins
Keyword: aquarium pump, recirculation pump, summer brewing, temperature control
Yield: 1 Temperature controller
Cost: 1000


  • Aquarium pump (desert cooler or any water pump would do) I am biased towards 12V equipment but 220V pump should be be good.
  • Tub or a large mouth shallow container.
  • Ceiling fan ortable fan for evaporative cooling.


  • 2 m Rubber piping and tubings This will not be in contact with food so pick whatever is easily available at fits the pump
  • 2 kg ice
  • 1 towel old towel or cotton t shirt is fine


  • Put fermenter in a big tub. Tub acts as a collection vessel and prevents spillage of excess water
    fermenter in a water tub summer brewing
  • Take an aquarium pump and place it in the tub. Submissible pump the is best as they are sealed. I prefer 12V as there is no fear of 220V main power to electrocute you
    aquarium pump
  • Attach tubings. Connects the pump to the top of your fermenter. Remember, pump has to circulate chilled water from base of tub to the top of your fermenter. Submissible pump has only water outlet (the pump can directly be places at the base of your tub.
    tubing for fermenter cooling
  • You can make a ring of the outlet pipe so that it can easily rest at the neck of the fermenter. You can seal the end with a clip and make holes so that the water showers uniformly across the ring. But be careful that water does not spray outside the tub otherwise it will be one slippery mess. Use a hot nail to pierce the tube or you can use a 1mm drill to make holes.
    sealing the tube fermenter cooling with holes
  • Add tower. The tower will soak water, so that the water evaporates and chills the fermenter (it works in the same desert cooler principle) .
    Summer Fermenter with water cooling


Possible upgrades:
  1. You can attach a timer or Thermostat so that the pump does not operate the whole time.
  2. If you pass the outlet pipe through an ice bucket or your refrigerator, it can operate for a whole day without any intervention.
We ran a small experiment with a vigorously fermenting beer. Typically the wort (fermenting liquid) temperature is 3-5 degrees higher than the room temperature (due to yeast metabolism) However, in this case, the temperature was 7 degrees lower.
Room temperature was 33C, water bath was at 25C and the wort temperature was 26C (the towel was the coolest as the fan was cooling it down through evaporation.
Bad news for Chennai and Mumbai brewers. Being an evaporative cooling, it works best in hot summers (and not in humid rainy season). 


Swamp Cooling Homebrew Beer Carboy Water How to Ferment Cover Carrier



    4 stars
    This recipe looks to be good but I am brewing my first beer and have ordered the following ingredients Malt Extract (Instant Beer Wort powder), Yeast Nutrient DAP..50gm, Beer yeast- Stout Porter 5gms, Hope pellets – Magnum 25gms. So how do I go about it ?

  2. 3 stars
    I am yet to get the deliver of material I ordered. Pls use better service provider for delivery

  3. Robin Soni

    Thanks ji
    You can get even better result in ac room where ac is used only at night

  4. 5 stars
    Thank you sir. Your engineering solutions are always top notch

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