Make a DIY Bucket Air Conditioner

Make a portable room air conditioner for about $30 with a couple of buckets and a desk fan

The bucket air conditioner at work

(TL/DR: Click here to skip straight to the instructions)

We have central air conditioning. It’s a big, hulking monster from the early 1980’s that’s loud, doesn’t cool well, and practically forces us to take a second mortgage on the house every time we run it for a couple hours, so we rarely use it. Mostly we sweat it out with fans and shades.

A few days ago, my wife came home from the neighbors to tell me about their portable swamp cooler which kept their house pretty comfortable even though it was almost triple digit heat outside. I investigated and found that it was an “evaporative cooler”, basically a box that blew air across water to cool the temperature of the air. Units for a room the size of my family room ran about $400, which was the same cost as a portable AC, so I figured if I was going to spend $400 on a portable unit, I’d spend it on an AC.

But I didn’t want to spend $400 on anything, so I decided to wander the Internets and see what kind of DIY swamp coolers were out there. Turns out, there’s all kinds, many of which worked the same as commercial evaporative coolers, but cost far less.

A little more research led me to rule out the coolers that called for pumps and trays and evaporative media because I would have to buy all that stuff. Instead I went with the “bucket AC”, which uses a couple of buckets, a fan and some plastic pipe, because, other than a cheap table fan, I had all the stuff.

Most of the bucket AC instructions I came across called for a 5 gallon and 3 gallon bucket and some 1½-inch PVC pipe. The room I wanted to use this in is a little larger and has high ceilings, so I went with a 10 gallon and 5 gallon bucket and 2-inch pipe (also, I already had the buckets and the pipe).

Building the Bucket Air Conditioner

Supplies

• 2 buckets — one 10 gallon with lid and one 5 gallon (or 5 gallon with lid and a 3 gallon)
• 2-inch PVC or ABS pipe — I went with the black ABS (used in drain vents) because I had it leftover from a sink project. You need about 36-inches.
• 1 desk fan — Size will depend on your big bucket’s lid size. Mine was 12-inches in diameter, so I got a cheap 11-inch desk fan from Amazon.com
• 1 gallon jug of water — Chill it in the fridge or freeze it overnight

Supplies – 10 gal bucket, 5 gal bucket and pipe

Basic 11-inch Desk fan

Tools

• Drill
• ½-inch drill bit
• 2-inch hole bit
• Small hacksaw

Step 1 – mark and drill your holes in the large bucket

Drilling holes in the side of the large bucket

Step 2 – drill holes in the smaller bucket

Smaller bucket inside the larger

Using 2 wood blocks to hold the smaller bucket in place

Place your smaller bucket inside the larger one and align it so it’s in the center. Use pieces of wood or piping to keep the smaller bucket centered in the bigger one. With the three holes in the big bucket as guides, use the hole bit to drill three holes in the smaller bucket.

Step 3 – Cut and insert your pipe

Cutting lengths of pipe

Pipes inserted through the bucket holes

Cut three even lengths of pipe and pass them through the holes in the buckets so the ends stick into the inner bucket just a little. I originally cut mine to 8-inches, which was more than long enough to pass through both buckets, but I found slightly longer pipe length of 10-inches distributed the cool air better.

Step 4 – Cut a hole in the big bucket’s lid

Using a drill bit and some string to trace the lid cutout

Drilling the hole for the saw to cutout the lid

Cutting the hole for the fan

You want to cut a hole big enough to allow the fan to blow the most air it can into the bucket without actually falling into the bucket. My 10 gallon bucket’s lid was a little over 13-inches in diameter inside the rim, so I bought a basic 11-inch desk fan from Amazon, which, conveniently, was 12-inches wide with the fan guard.

The easiest way to trace the piece to cutout of the lid is to push a drill bit in the lid then use a piece of string and a pencil like a compass. Once the outline is traced, make a hole at the edge of the line, pop your hacksaw blade through the hole and follow your line with your saw to cut the opening.

Step 5 – Try it out

Two 1 gal jugs of chilled water in the interior bucket

The bucket air conditioner with the fan in place

Once it’s in place, put the jugs of chilled water in the center bucket (I can fit two in mine), flip the fan face down on the bucket lid and turn it on. Viola! Conditioned air!

My results

Is it possible to keep the house cool in a triple digit heat wave with a bucket air conditioner?

Yes. Absolutely.

Our usual strategy in a heatwave is to leave with the windows and doors open at night to let in the cool air, then close the house up in the morning before it starts to heat up. With just a couple of circulation fans, we can usually keep the temperature below 80 degrees until noon. By mid-afternoon indoor temps creep into the mid-80s and don’t start coming down again until it cools off at sunset.

(l) Outdoor temperature, (r) indoor temperature

The first day we tested the bucket AC it was around 70 degrees at 7am but it was expected to reach the high 90s by noon. It hit 80 degrees a little after 8am (hello sunshine) and we followed the usual protocol, closing the doors and windows. Then I switched on the bucket and let it run.

As you can see from the nearby photo, 30 minutes before noon the outside temperature was heading for 100 degrees while the indoor temp had moved a mere 2 degrees. Better yet, that weather station is near the front door in the living room, a good 35 feet from the bucket, which meant the whole front section of the house was similarly comfortable.

We managed to ride out the 5 days of that heatwave with the indoor temperature never climbing above 82 degrees, which is pretty good results for an AC unit built out of buckets, water jugs and a desk fan. It definitely works and works well.

Lessons Learned

It’s not so much about the cooling, as it is slowing the heating.

In my system, two gallons of water chilled down to 40 degrees reaches room temperature — whatever that is, 70, 72, or 80 degrees — in a little over 2 hours. The room temperature never falls, so it’s not cooling it, it’s just slowing the rate it gets hotter. Without the bucket AC the indoor temperature rose about 2 degrees an hour. With it, it rises at less than 1 degree every 2 hours. As a result, if I want the room to still be a warm (but comfortable) 78 degrees in the late afternoon, I need to make sure the room is as cool as possible in the morning and be ready to fire up the bucket AC as soon as the outdoor temps start to rise.

The bucket air conditioner chilling in the family room

That said, the $20 I spent on the fan and the afternoon I spent putting the bucket air conditioner together were well worth it. Even if it looks like R2D2 with battleship guns, it does a pretty good job at keeping the family areas of the house comfortable, and it’s way less noisy and expensive than my old beast AC.