DIY DWC Chiller

I retired in 2018. I been growing, again since then. My first set up was a 2.5 x 2.5 x5 tent. DWC bubblers, 3 5gal buckets, blurple leds, 4" exhaust, intake fans filters. My son got me into bubblers after going to Amsterdam in 2009. The first problem spotted in my environment, basement, was nutes getting too hot. Bubblers pumping ambient heat. So a chiller was necessary, but…
Having three separate buckets, I wanted a system that was clean, easy to manage, and cooling without a reservoir and circulating pumps to deal with. I experimented with the chiller itself, failed and ending up using the simplest method. A water bath(coolant) chilled to ### temp; pump feeds coolant to bucket radiators and back to bath.
Borrowing from brew geniuses, the system uses a stainless steel wort chiller per bucket.

I got a 3.5 cu ft chest freezer at my local appliance store for $140. I found a (16 gal) tank to fit for ~$50.
The tank was cut to fit and holds 12 gallons. Now the expensive part. The coolant is 50/50 propylene glycol/water. The coolant is 50/50 water/propylene glycol(~$100). This will allow the coolant to get below 0ºF without slush.
1/2" tubing, a small 12v pump for circulation. A voltage speed controller is recommended. Star distribution to the buckets. I have shut a off valve to one bucket. A temperature controller with probe controls the temp. Pump is on when the high temp threshold is met. Off when low is met.
I have been using this since I fist saw the temps go up and it’s been the best time saver for me.
I now have a 4x4 with the same set-up going. Still use 3 individual nute buckets. Brighter lights, co2, humidity control, have never saved me as much time as keeping the food nice. It gets a little taxed in summer with sweating and cycling. The speed controller allows the coolant flow to be adjusted.
I know this is not feasible for everyone. The freezer cost about .5Kw per day. I think the bubblers cost that. Happy growing. Peace


@newVesuvius - I love your system.

I have a few questions. You said you didn’t want to deal with reservoirs and circulating pumps for the nutrients into the buckets.

Wouldn’t it have been easier to have a reservoir and a pump for the nutrients, then cool just the reservoir?

Second question - do you find that you are chilling too much? Because a freezer is below freezing, but you really only need to cool it down to 70 degrees?

Really appreciate you putting this up here for us to see.

Hi Medmaker. I am sure there are easier, efficient ways. This is by no means a precision exercise, but a way to keep the temps relatively safe. I am running a small set up with 5 gallon buckets. Getting older than I thought, and I’ve decided to stay with individual buckets for simplicity, mobility. I can clear the tent quickly. So a reservoir was out.
2. Using these wort chillers, the surface area is only about 3%, volume of coolant in lines ~ a cup. With 3 buckets, there is 7.5 gallons to be cooled by some small radiators. It’s a matter of heat tranfer. The heat is being drawn away by the flowing coolant, dumped into bath. It took a bit of experimenting.
Flow rate of the coolant needs to be adjustable, and temperature as low as reasonable.
As the buckets chill, the bath heats. The temp needs to be low enough, that it can keep up. If not cold enough the bath water will equalize with the nute temp (bigger bath is better), and be ineffective until the freezer could cool it down. It’s a temp buffer. In the winter, it runs itself. In the summer, it takes some monitoring, adjusting. Needs a defrosting too.
I’m not an expert at this but trying. Thanks again. Peace.

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@newVesuvius - thanks for the reply! I understand the issues, you explained them clearly - thank you!

I hope I don’t get to where I need a freezer/chiller, but I’m glad you shared this so I know what to expect.

Well, if you do have a need and are using RDWC, your idea would be the way to go. I would get a commercial unit if I did it that way (more reliable and cheaper). I couldn’t find a solution to fit what I wanted. I used to be a lab rat, so it was a fun project.
Happy growing. peace.

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May I suggest
Are my calculations right? - #51 by Ashleyroachclip 36 month pay off I’m ordering 2 of them for my 2 bucket system 4x4 tent. Go find me page…lol

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Tdubwilly did something similar with a discarded apartment refrigerator for his cooler. Neat idea. Where I lived before, my grow space was in the garage, with an east-facing wall in perpetual shade. I’d thought about simply digging a hole 4 feet down, dropping a coil of copper tubing down there and running some kind of heat exchanger like you did. Instead I just bought a chiller lol.


You might find some interest in this thread… :point_up::+1::wink:


LOL my first attempt was a fridge with 150 ft of copper coil. Expensive learning process. I didn’t think of the pressure required to push coolant thru all that copper. Kept blowing out the line and pumps. Hence, the bath. Now I have a lot of scrap copper and fridge. I did this when I thought I was able to make anything. I’m somewhat hobbled now. I have definitely learned the value of planning from my failures.
+++ for the chillers. Thanks for memories and Peace!


This is almost exactly what i plan on doing but i will run the freezer on a temp controller instead of the glycol (really cool idea tho… and now that i think of it i have another res buried underground that i need to cool and doing it this way might let me pull off both at once…i will have to try it in a few months)

Thanks for the really awesome thread 0_o


He may have been referring to this thread @fano_man:point_up::wink::+1:

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That’s a really cool system… so does the lid on that close? And does it just stay liquid and just runs water through it… if it’s not moving does the water freeze in the lines?

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Thanks, fano_man, the lid closes. The coolant is 50% propylene glycol, 50% water, good to ~ -30ºF, so the lines don’t freeze, but they do sweat, frost some. @anon4427090, if you have a large freezer/bath, you may get away with only water. Depends how much you have to cool. The pump only runs about 2 minutes when needed.temp control Thanks peace.

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I have a 40 GAL (I dunno… big enough for two annoying people anyway.) deep freezer i can use.

It would ideally run a subterranean RES that i keep around 20-40 GAL (it stays near 68-69 on its own tho but why not? 0_o) and a 120 site clone machine i am insulating day by day …when i pass by i grab another can of great stuff and unload it behind the thing and do it again next time… temps get better everyday lol (No clones were harmed in the screwing around of this project.)

I think i am gonna try filling it with water and putting the exact same temp controller you have on the freezer to keep the water at 34F and another controller on each res individually… if i cant keep temps down without a lower temp to buffer i will go the glycol route when i redo everything after this round.


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Excellent! sound like you got it. peace