Build A Homemade Swamp Cooler For Your Grow Room

If your grow room is getting too hot or the humidity is too low a homemade swamp cooler may be just what you need to help control your growing environment.

Air conditioners are expensive to buy and run and they can be noisy too. I needed to do something about the temperatures in my grow room but an air conditioner just wasn’t practical for my situation.

Also when the lights are on my humidity is very low at about 20-25% and an A/C would just make this even worse and require adding a humidifier and I don’t have room for both. I decided to try a homemade swamp cooler

Thankfully a diy swamp cooler not only takes care of both these problems, but can be silent, is cheaper to run and very easy to build. I already had a spare fan and a bucket so all I needed was to buy an evaporative cooler pad which cost me about 15 bucks.

Here are a few pics of my homemade swamp cooler:

Homemade Swamp CoolerThe first pic uses a 4 inch Soler and Palau TD 100x that moves 100 cfm and is whisper quiet. Read my review of the soler and palau tdx 100

diy swamp cooler
This picture uses a Hydrofarm Active Air 6 inch In-Line Fan rated at 400 CFM. BTW the fan is upside down in this picture but you can see it fits very nicely on top of the bucket.

How did my diy air cooler work? Well in a room that was 79 degrees it was putting out 68 degree air at 77% humidity. Inside my grow room the temps don’t get above 82 and the humidity stays in the mid 30s with lights on and mid to upper 40s with lights off.

My temps have been too high. I run 2 600 w blockbuster hoods and a 300 cfm fan. I run at night when it is cooler but even still in the summer when it is hot outside temps can get into the high 90s.

The plants can handle it just fine but my buds are not as dense as they should be for my summer grows. Also plants cant breathe right when humidity is too low. This makes them have to drink more and work harder and affects yields.

These numbers are for the small tdx 100 fan. The active air fan is a beast and I am sure it would do better but it is too loud for a stealth grow in an apartment. I have a tdx 150 its really quiet and am using it for an exhaust fan and moves 300 cfm. I will use to update this homemade swamp cooler. But before I do I will be replacing it with a td 200 that moves 538 cfm. I expect this will give me another 10 degrees of cooling.

Here is my homemade swamp cooler keeping some young Biker OG Kush cool:

my swamp cooler keeping some young Biker OG Kush cool

Swamp Cooler DIY – How To Build A Swamp Cooler


I looked online and found several homemade swamp cooler bucket videos and designs. My first diy evaporative cooler followed these plans but proved to be inadequate for a grow room. For one thing the bucket didn’t hold enough water to get through a 12 hour cycle and pulling the lid off to refill it was a royal pain in the ass too.

After thinking about how to build a homemade swamp cooler that would work for my grow room I came up with the idea to place a bucket inside an 18 gallon Rubbermaid tote. This gave me plenty of water. Originally the pump was inside the bucket and I couldn’t accurately tell how much water was in the bucket either. So I placed the pump inside the tote where I could see it and make sure it wouldn’t run dry. I am using an Eco Plus pump rated at 300 gph. I am thinking I may want to replace it with the 400 gph model.

To build your own homemade swamp cooler you will need:

  • 5 gallon bucket
  • 5 feet 1/2″ tubing
  • 300 – 400 gph eco plus pump
  • 1/2″ tee fitting
  • 18 gallon Rubbermaid tote
  • 100 CFM or better fan
  • filter pad
  • zip ties
  • ducting – optional but can be used to direct air flow

I will post links to Amazon below these pictures so you can buy this stuff. You may already have everything you need but the evaporative cooler pad is hard to find.

First you will need to cut a length of tubing and connect it together with the tee fitting. Make it a bit smaller, maybe 1/2 to 1 inch smaller than the inside diameter of the bucket. The actual size is not critical.

I drilled 3/16″ holes every half inch around the bottom and also around the side of the tubing that faces in. You can play with is spacing or the hole size if you want. The important thing is to get an even flow of water dripping down the pad.

evaporative cooler padHere is a picture of the pad. You can see the tube going down into the bottom bucket and out through the holes in the very bottom of the bucket. The pad I bought was large enough to do 2 buckets. It was hard to cut with a razor so I used a pair of scissors instead.

cooler pad with tubing installedThe pad is folded over the loop of tubing and secured with zip ties.

Pump on bottom of cooling padPump on bottom of pad. This pic is from my first prototype. If you want the pump in the tote you will need a longer piece of tubing than this.

pic of the drilled out bucketHere is a pic of the bucket. It’s not pretty because I used a cheap hole saw that tore as much as it cut. The hole size isn’t important but you want a lot of air to be able to pass through the pad.

pic of the bucket holesThere are 2 holes in the bottom of the bucket to let water in from the tote and you can see the tubing the pump will be attached to.

looking down the centerA look down the center of my homemade swamp cooler. The pad kept sagging down so I eventually zip tied it to the sides of the bucket so it would stay all the way up. bucket and pump sitting inside the toteHere is a picture of the bucket and pump sitting inside the tote.

bucket lid with hole for fan cut outThe lid is snapped on and you can see it fits up against the top of the cooling pad. I cut the 6 inch hole for the fan with a razor. This lid had rings in the center so all I had to do was follow them and I got a really good cut out for the fan.

I love these Eco Plus pumps. They are cheap and run forever.EcoPlus 728310 Eco 396 Submersible Pump, 396GPH

This pad is like a plastic foam and can make 2 swamp coolers. It’s cheap but hard to find and better than paper pads some coolers use.

Dial Mfg. 3072 Dura-Cool Pads

I love Soler & Palau fans. They are extremely quiet and can be set to run on 2 speeds. This one is the Soler & Palau TD-100X it is 4″ puts out 135/100 cfm

Soler & Palau TD-100X Inline Exhaust Fan

The 6 inch TD 150 puts out 293/218 cfm

Soler & Palau TD-150 In-line Exhaust Fan

This is a 6 inch Soler & Palau TD-150S. The S stands for silent and it has special baffling that makes it a super stealth version from the Soler & Palau Silent Series that puts out 333/239 cfm. It cost more but if stealth is your goal this is the quietest fan you will ever find.

Soler & Palau TD-150S In-line Exhaust FanIt moves a lot of air very quietly. It is a great grow room fan too and I actually use the 8 inch version in my newest grow closet. It really is super quiet and keeps my temperatures way down so in my larger closet I don’t even need a swamp cooler.

Enjoy Building Your DIY Swamp Cooler

Building a homemade swamp cooler is a great project. It is simple to do and relatively inexpensive. You can tweek this design to fit your grow room. You can change fan sizes to fit your room. My room is small, 3 x 6 but even with a small 100 cfm fan I am getting 10 degrees of cooling.

Please remember that these are evaporative coolers and not air conditioners. They work best in low humidity situations. The lower the humidity in your grow room the better they will work.

Here is a quick video tutorial I made on building a swamp cooler:

So now you know how to make a homemade swamp cooler for your grow room. Go forth and chill!

2 thoughts on “Build A Homemade Swamp Cooler For Your Grow Room”

    • The fans need to suck air from the bucket. The air passes through the wet filter pad via holes in side of bucket and out through the other end of the fan. If you reversed it you would be blowing the water out of the bucket.

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