Swamp Cooler




Introduction: Swamp Cooler

I don't know what the common perception of Canada is, but let me tell you it's not all igloos and polar bears. I live in a region that is one of the hottest and driest in the country. The temperature in the summer usually reaches 40 degrees C (104 F) and it is dry as a bone. We live in an apartment with one small wall mounted air conditioner, and it just can't keep up, at least not without running up the power bill. I've tried a few experiments to see what kind of cooling effects I could add to the living space, but nothing has really panned out as good as I had hoped, and I have wanted to try an evaporative cooler for a while. A few years back I went to school for mech. eng. technology, so it's now time to put it to good use.

I learned the principles behind hydronic cooling, swamp coolers and chilling towers and the like, at school, so I had a good grasp on it already. I always look to instructables before doing any projects to see if there are any good plans or inspiration that I can use right off the bat, but I was surprised to find very little, so of course my design brain engaged and I set to making my own swamp cooler.

Step 1: Design

I am not the kind to start something without a plan, so I like to get my brain going before my hands. The design will be simple, a case to house the cooler, a pump, a fan or bank of fans, and a medium for the water and air to interact. Right off the bat I'm thinking a screen on the outside (I really don't like bugs inside), then the fan, which pushes the air across a drip panel made of porous material, and a pump at the bottom circulating water up from a reservoir onto the top of the drip panel.

I measured the size of my window and designed the box to fit. I started with a model of the housing, since that would be the first thing I will build then fit the rest of the parts inside that. I wanted to be able to access the inside of the box while it is still sitting in the window, so the inside grill needs to be removable.

I found a 110V bath fan at Princess Auto for $5, and a couple of those should do more than enough to move the air. A small pond pump will also move more than enough water for this project, since all you need is to keep the evaporation medium wet, and that keeps everything running on 110V and I can wire the unit to use just one power cord. The plan for the pump is to use a small pond or statuary pump, again using 110V.

Step 2: Tools & Materials

Working with sheet metal isn't easy if you don't have the proper tools. For that reason this isn't an easy project. If you don't have a way to bend sheet metal you will have a hard time with this, I made myself a sheet metal break just for this project (you can find my Sheet Metal Break instructable on this site, but I can't for the life of me figure out the freeking hyperlink). You need pretty well stocked metal shop to work with sheet metal, I guess an alternative to bending would be cutting out each flat piece and welding corners together instead of bending them, but as a hobby welder working with thin sheet metal can be difficult. That being said, here is the list of tools I used to make my swamp cooler.


Marking tools

Sheet metal shear

Sheet metal break


Drill press

Various drill bits & taps

Table saw (if you need to rip your hardwood pieces)

Chop saw

Staple gun

Soldering iron

As I said before there are ways around needing these tools, instead of a shear you could use a grinder to cut your pieces, but it would be slower and dirtier. You can also use a drill if you don't have a drill press.


Sheet metal


Pond pump

Bath fan (x2)

Humidifier evaporation pad (x2)

Angle brackets

Speaker cloth

Hardwood scraps

Spray paint

Extension cord

Various sizes of heat shrink tube

The finished housing will need to be painted, powder coating would be the best option because then there's no way that the paint will come off to allow the metal to rust. It is expensive but it's the best way to paint it, so, due to budgetary constraints I of course went with spray cans.

Step 3: Build the Housing

Start by laying out your flat patterns on your sheet metal, as long as your bends are simple laying out the flat pattern is easy. Cut out your pieces using your shear; if using a grinder make sure you account for the added thickness of the cutting wheel. I cut out my four box pieces first, but I'm sure there will be other additional pieces to cut out later. Drill a hole in a convenient location for your power cord, mine was on the right side near the bottom, but high enough not to interfere with the reservoir.

After cutting the pieces you need to bend them, this is where my pride and joy comes in. I made my sheet metal break for this exact purpose. The bends on the outside of the box are primarily to give the box strength, but also to hold in the screen on the back side, and a screen or air filter on the front.

Tack weld the corners to get your box together, then finish welding everything. After welding the housing I used a grinder on the outside of the welds to smooth out the surface. I also made the reservoir at this time, using a square piece of sheet I bent it into a channel and welded two end caps on. The welds on this have to be water tight so be careful.

After everything was welded and cleaned up with the grinder I needed to paint the whole thing. Since water will be all over this thing, I didn't want any issues with rusting. I started with red oxide primer then a top coat of white spray paint. I think it looks pretty darn good.

Step 4: Install the Fans

I had to find a way to attach the fans to the inside of the housing, which was a bit tough because there wasn't much on these fans in the way of a frame. I was able to use the 2 little screws that attach the motor into the iron core of the fan, mounting two flat arms that extend out to the sides of the box. I wanted to use fasteners instead of welding onto the housing so that it would be easy to remove all the internal pieces if need be. Make sure you use stainless steel fasteners so you don't have rust issues. I welded angle brackets onto the ends of my fan arms, and drilled corresponding holes in the housing sides to mount them. Paint the ends of the fan mounting arms to keep them from rusting.

I ended up not using a screen on the outside of the swamp cooler, because, it would be sitting in my window that has a perfectly good screen of it's own, but I did mount the fans far enough away that a screen could be added later. I held the fans in place where I wanted them and marked the locations of the holes on the housing. Use a drill for these holes since it's easier than a drill press on the welded housing.

Step 5: Install the Evaporation Medium

The swamp cooler needs a medium where the water can make contact with plenty of air in order to easily evaporate. This also happens in a humidifier in pretty much the same way, so I decided to use a replacement humidifier pad. I found a replacement humidifier pad at Home Depot for $13, so I got 2.

This step goes hand in hand with installing, or at least mocking up, the reservoir. I wanted the bottom pad to hang down inside the reservoir so there would be no splashing or dripping from the water falling into the reservoir. The water level will stay below the bottom of the pad, but it is shielded by the reservoir.

The pads are layers of expanded aliminum mesh stuck together adding up to about 1.5" thick. It's easy enough to bore a hole through the pad on the drill press for a screw in each top corner. I measured and marked the inside of the housing for where to mount my brackets, with the fans in place so I knew I had enough clearance. I used some larger angle brackets and threaded one of the holes to receive a 1/4"-20 machine screw and used that to secure the pad with a long screw and a flat washer. Again, use stainless fasteners.

Notes: I glued (epoxy) my reservoir on top of a pressure treated 2x6 so that it would be stable but could still be removed from inside the housing. Make sure you account for the 1.5" difference in height with this set up.

While testing my swamp cooler I left it running for a while and when I came back it was blowing bubbles. It would have been fun if I had a 6 year old, but alas, no such luck. I figured out that the humidifier pads came coated in some sort of oil. It turned the water brown and slick, so I emptied the cooler and washed the the reservoir and pads. I rinsed them until the water came out clean, because you don't want any soap left on them either.

Step 6: Install the Pump

I originally wanted to use a pond or statuary pump for moving the water, because then everything would be running off 110V and I could just wire them all up together. The first pump I tried was a low flow pump and couldn't pump the water up the measly 3' that I needed. I looked around for a more suitable unit but there was nothing available is stores, being that it is nearing the end of the summer. Because it was nearing the end of the summer, I also didn't want to order another pump online and wait for it to be shipped, so I instead opted for a 12VDC bilge pump I found at Princess Auto. THis meant I would now have to have a power transformer in the cooler.

I ran some 1/4"ID tubing up from the pump in the reservoir to the top of the evaporation pad, and made a little manifold with a few 1/4" fittings to split the water into 3 streams to flow back down to the reservoir. You could do more to try cover more of the pads at the top, but 3 is definitely sufficient. The pump just sits in the bottom of the reservoir under the evaporation pad and the tube and power cord run up the side. The tube is zip tied onto various brackets to keep it where it needs to be.

Step 7: Wire It Up

I could have hard wired everything together and soldered all the connections, which was my original plan before I had to change my pump, but this way has proved to work just fine.

I cut about 16" off the female end of a block heater power cord (3 plug splitter) so I could run it through the hole in the housing, and then I soldered it back together on the outside of the box. I always use heat shrink tube when soldering cord connections, especially in this case it keeps the water out, and it just looks nice and clean. The fans had a standard plug on them so they just plug right into the extension cord, but the pump needed a transformer. I have various wall warts kicking around my electronics bin so I used one that was rated at 9VDC and it works perfectly. I soldered the wall wart to the bilge pump and plugged that into the final spot on the cord. I recommend putting a drip loop in the pump cord, with the soldered connection at the top, and the cord drooping down before coming back up to plug into the extension cord. This will keep any water that happens to get on the cable away from the connection at the top.

As a side note, I have a remote controlled switch that I can plug into the wall so that I can turn the swamp cooler on without having to go plug the unit in every time. Very handy.

Step 8: Close It Up

After testing and making sure everything works as it is supposed to, it's time to hide the unsightliness that is this swamp cooler. I didn't remember to take any pictures of this, but it is a pretty simple step. I used some pieces of maple to make a frame that would fit around the outside of the housing on the front, glued and pinned the corners. You should use hardwood whenever water is present because it stands up much better, but I suppose it's not entirely necessary. I had some so I used it. After the frame is made, I laid it face down on some speaker cloth and wrapped it around the back where it was stapled. I made my frame a bit too big so that I could wrap the cloth all the way around the wood piece and this gave the frame a good friction fit over the housing. Speaker cloth is porous so the air will pass through but you can't see through it very well. In the end it looks really quite good.

Step 9: Finished Product

There is the finished unit. I put a couple little wood shims on the window sill so that it sits nicely in the window. And my wife even thinks it doesn't look so awful (one day you think she would stop being so surprised). I haven't done an official measurement, but the air coming out on the inside of the building is definitely significantly cooler than the air outside. We haven't had a hot dry day since I finished the cooler, so it hasn't been as efficient as it could, but it is definitely working. The fans don't move too much air, and they also have to push the air through the thick evaporation pads, so it doesn't move a lot of air into the room, but over time it will no doubt make a difference.

You will want to be careful when reloading the cooler with water, ideally you would want to use distilled water, but that's just ridiculous, so just make sure it's clean, no oil or soap.

That's it, enjoy your cool air.

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    2 Discussions

    You could put the electric plugs in some kind of junction box made from a crayon box and sealed with silicone glue.