Introduction: Portable Evaporative Cooler (swamp Cooler)

Picture of Portable Evaporative Cooler (swamp Cooler)

In areas with low humidity, regular air conditioners don't work very well. A simpler solution uses water evaporation to cool and humidify air. These are called evaporative coolers or swamp coolers and are used in homes all over the Southwest U.S. Air is pulled by a fan across a wet pad, which lowers the air temperature by 20-30 degrees, and provides much needed humidity as well.

We attend a week-long festival in the remote Nevada desert, where daytime temperatures climb well over 100 degrees F.In this situation, it is necessary to be completely 'off the grid', self contained, and self reliant. In order to remain comfortable, we made portable swamp coolers out of common materials, powered by solar panels, to cool our enclosed living spaces. They have also been used at home in more permanent installations to cool greenhouses. Additionally, they could provide temperature regulation to desert homes where electrical power is not available.

Step 1: Materials

36-44 gallon heavy duty trash can with lid
Evaporative cooler pad x 12 feet x 29 inches
Hardware cloth or chicken wire x 6 feet x 24 inches
Submersible 12 volt bilge pump x 1
1/2 inch irrigation tubing x 10 feet
1/2 inch T-connector for irrigation x 1
Automobile radiator fan or solar fan x 1
16 inch diameter HVAC tubing
Large drain pan
U-bolts x 3
Solar panel and deep cycle battery

Step 2: Examples of Materials

Picture of Examples of Materials

With the exception of the fan (and solar panel if you use one), most everything can be found at a Big Box Hardware-type store (Lowes, Home Depot, etc). Much of it can be scrounged for free, as well, if you are patient and resourceful.

Step 3: Assembly

Picture of Assembly

First you need to make a way for the air to pass thru wet padding:
Cut 2.5 inch diameter holes in sides of garbage can. A drill bit made for cutting doorknob holes works perfectly.  Leave the lower 10 inches of the garbage can intact, without holes. Line the inside of garbage can with blue evaporative cooler padding x two layers. Keep it in place with hardware cloth or chicken wire on the inside. Keep that in place with the U-bolts drilled thru the garbage can sides. Now you have a garbage can with ventilation holes, lined with evaporative cooler pads which are kept in place with hardware cloth wire.

Now you make a dripper to keep the padding moist:
Make a circle with the 1/2 inch diameter irrigation pipe; join with a 1/2 inch T-piece. Drill very small holes about every 2 inches in bottom side of circle for water to drip from. (If you want to get really fancy, you can insert drip irrigation emitters in the holes, which will give you a known gal/hour drip rate. )

Now we need to get the water up to the top of the pads:
Place 12 volt submersible pump in bottom of garbage can. Connect the pump to the drip ring with 1/2 inch tubing. Feed wiring thru one of the holes so you can connect to battery power later

Next, we need a fan at the top, which will suck air in, thru the holes in the sides of the garbage can, thru the evaporative cooler padding, and out the top into the HVAC tubing which will deliver cool, humidified air to the location of your choice:
Cut out a circle in top of garbage can lid and mount fan.Make sure it blows upwards! Used auto radiator fans are cheap, blow lots of air, but use a LOT of amps. So we eventually bought a solar-type fan for about $200 that runs forever on a 45 watt solar panel hooked to a deep cycle 12 volt battery. An auto radiator fan  will use more juice than this system puts out, and only runs about 20 hours before draining the battery faster than the solar panel can charge it. However, if you have enough solar panels, the auto fans REALLY put out lots of cool air, compared to just a breeze from the solar-type fan.

Wire it up! Soldering connections is a good idea, but you may want to make the wires to the top lid/fan/HVAC tubing component unpluggable so they can be removed for easier packing for transport. I also installed a switch to cut off the pump in the cool morning hours and just have a fan. It gets too cold, otherwise!

The entire unit will need to sit in a catchment basin, to collect water that drips out from the sides (this dripping is inevitable). Big black tubs from a garden center work well. you may need to drill holes in the bottom of the garbage can to allow this water to percolate back inside to the pump.

Step 4: Where Stuff Goes

Picture of Where Stuff Goes

First photo shows completed body without top.The next three views are looking down into the cooler, showing the pump and drip tubing. Next is a view of the top with fan installed. Then, a view of the whole thing put together, and one of it in use. Solar panel is not in view.

Step 5: Running It

Picture of Running It

You'll need about 6 gallons to fill it and wet the pads. Afterwards, uses about 2 gallons/hour, depending on the humidity and temperature. More holes in the drip ring may lead to more water usage. And that's why the emitters might help decrease water use. For home/permanent use, install a toilet float valve hooked up to a permanent pressurized water source.

Step 6: Swamp Cooler in Action in the Nevada Desert

Picture of Swamp Cooler in Action in the Nevada Desert

The camper is called a Flip-pac, the sleeping area is over the cab of the truck. The swamp cooler HVAC tubing is directed to our sleeping area. The solar panel (it is pretty dusty, here) keeps the deep cycle 12 volt battery charged. The battery provides a consistent flow of electricity to the swamp cooler pump and fan. By the way, the green structure behind the truck is our fancy shower.


wyocoyote1 (author)2016-06-05

I attend more n likely the same hot dry dusty gathering. Many years we have lucked out and had some 110 to run AC's or wall plug swamp coolers. Not so this year at Chilleville. Your unit is mondo and your awesome flip pac camper with the requisite silver bubble insulation probably has similar cooling needs to my Alaskan pop up camper. How many Gallons of agua are you going through on a typical blistering playa day nap? Or lets just keep it per 24 hours average. I was thinking a 5 gallon bucket or ice chest style within my camper might do the trick. I wonder if there is a cooling advantage or disadvantage to having your evap cooler inside rather than outside. Better brush up on thermodynamics. I guess at some point the humidity inside a structure would make it so the cooling effect of evaporation was diminished. didn't notice this when using a plug in one inside a van one year. Is Bill Nye a burner? Very interested to know how much H20 your mega swamp consumes, gracias.

Mcginnstable (author)wyocoyote12016-07-01

It needs to draw in outside dry air to have continued cooling effect. Otherwise like you said, the humidity will just continue to build and eventually prevent evaporation.

willliamfriend (author)2016-03-27

What type of fan is pictured here? To me it looks like a HVAC condenser fan but those use a ton of energy.

Ranie-K (author)2010-08-01

Would this work for a house?

KittyF (author)Ranie-K2010-08-02

if you're asking if a swamp cooler works for a house, then yes, my brother lived in NM and used a swamp cooler to cool his house. His used a fan. If you want to be off grid with your swamp cooler you need a way to blow the cooled air throughout the structure such as this person used with solar panels.

Ranie-K (author)KittyF2010-08-02

Well, my question is if the air getting cooler (and will therefore sink) would be enough to make the air circulate: Inside air getting warmer, entering upper vent, entering swamp cooler, sink and finally enter the house again.

LouS (author)Ranie-K2015-04-22

You'll probably need a fan to get enough air circulation through the matting to make a difference. I doubt convection flow by itself will move enough air.

LouS (author)Ranie-K2015-04-22

No, you never want to recirculate inside air through a swamp cooler. All this will do is make the inside air progressively more humid and gain heat as the multiple passes reduce the efficiency of the cooler.

What you need to do is draw hot, dry outside air into the cooler, expell the cool, moist air into the house and then let it exit through an open window before it has a chance to heat up again. As it's expelled more cool, moist air from the cooler takes its place.

KittyF (author)Ranie-K2010-08-02

I'd think that question would depend on how large your space is, and how broken up (with walls or furniture) it is. FWIW, Kitty

Ranie-K (author)Ranie-K2010-08-01

Air is led from a vent near the roof in a insulated pipe into the swamp cooler, where the pipe (but not the house air) is in contact with the moist media. Evaporation make the air cooler and presses it down, trough insulated pipe and into an vent near the floor. Water is release into swamp cooler from mains or rain barrel as shown.

LouS (author)2015-04-22

Swamp coolers are indeed "one pass" devices. Draw dry, outside air into the cooler, exhaust the more humid, cooler air into the house. Then open a window at the far end to exhaust the air so more cool air can take it's place.

If you set up the swamp cooler to recirculate interior air, all you will do is load up the interior with humidity. Letting the humid air out and replacing it with fresh cooled air is the key to making a swamp cooler work.

north40nm (author)2014-07-07

very kool (see what i did there ;) am thinking to build one for my camper @ the burn this year... really 2 gals/hr? just run for the hotest part of the day i guess. cheers mate, and good job. a thought, if you had the mesh on both sides and made a cylinder inside the barrel, you wouldn't need the outer catchment? As the builder, you think that would work???

johnny3h (author)2011-08-21

@ Twoyellowdogs.  The output of any swamp cooler depends on two things:

1.  The Relative Humidity of the air it has to cool by evaporation, and
2.  The size of the unit [amount of SURFACE AREA through which the air is drawn].

I notice that your trash can hole pattern  leaves LOTS of un-cutout area.  I would guess you have about a 40 to 45% open area. 

Without changing ANYTHING else, IF you would either drill the holes larger so they ALMOST TOUCHED each other, OR drilled a lot more smaller holes in between, you would INCREASE the surface area of the matting for airflow, and thus INCREASE volume of cooled air created.

Ideally, like the commercial swamp coolers mounted on the Tucson rooftops, the wet mat area would be massive, with ONLY a thin metal framing to support the matting, hoses, and fan.

You could accomplish this by either drilling more holes, OR replacing the trash can with two layers of "hardware cloth" with the matting sandwiched between, and then just the bottom of the trash can at the bottom as a reservoir.  The double layer of say 1/2 inch hardware cloth would be more than strong enough to support the system, AND provide almost 100% exposure of the wetted padding to the air flow.

NO offense is intended as you have created a great cooler AND a great 'ible.

kanemaui (author)johnny3h2014-06-11

Aloha!!! EXCELLENT points, johnny3h! The original idea is basically pure genius, but with some of the modifications you mention, this system would be pretty stellar. But, seeing as how tooyellowdogs built this to be used in an area where the dust is almost as fine as baby powder (so I've heard from 'Burners'), not to mention, 'windy', the unprotected moisture matting may be subject to clogging from the random/fugitive dust flying around and collecting turning (possibly) into 'mud'. Just a thought ~ ~ ~ I plan on building one of these for a greenhouse/grow space in a high desert location where humidity is almost totally lacking ~ ~ ~ Aloha ~ ~ ~

anitagreen (author)2014-04-10

You have made a great swamp cooler, really nice design! But, I think it's not worth it spending so much money and time on this product as it would be not effective in extreme humid conditions. You should have purchased portable air conditioning instead which is great for humid for humid climates. Visit the following website for more useful information:

tooyellowdogs (author)2013-07-22

You probably need about 3-5 gallons to prime the system and get all the pads wet then about 3 gallons per day. We used cooler melt water (ours and as many neighbors as we could get water from) to supplement the amount of water we brought onto the playa.

jantonio8 (author)2013-07-20

I'm building one of these for the upcoming burn. How many gallows of water does it use per day/hour. As you know, it's not like we can go to the faucet if we didn't bring enough water.

bryan3141 (author)2013-07-11

would it help significantly to rig a tarp to provide shade over the cooler and the duct work?

Ericson578 (author)2013-01-30

How did the dust on the playa affect how the cooler ran?

tooyellowdogs (author)Ericson5782013-01-31

I did not notice any problem with the dust. Much of it is washed off with the water drip. There will be mud in the bottom pan, but not enough to bother the pump. I replaced the blue pads every 2 years.

bellinghammakerspace (author)2012-11-17

where did you get the giant ducting tube?

dropkick (author)2011-11-20

If your worried about humidity in your house you can sew some cloth sacks then fill them with kitty litter (the inexpensive clay type) and hang them up.
When the litter needs to be rejuvenated you put it in a pan in your oven for about an hour at 300F to 400F, let it cool and then put it back in the bags.
We've used this method for years.

If you want pretty you get a cotton print cloth for your sacks. If you want utilitarian you use canvas. If you're a bachelor you use tube socks.

Zombie_BBQ (author)2011-06-05

this is nice ,but only works in near zero humidity.i live in Tucson,Arizona swamp coolers are used every where .but if it gets above 25% humidity it wont blow cool air anymore.

johnny3h (author)Zombie_BBQ2011-08-21

@ Zombie_BBQ.  Since 1954, we have lived in SE Texas [on the Louisiana border, AND ONLY about 8 or 9 miles in from the Gulf of Mexico. We DO HAVE HIGH HUMIDITY!!!!!

Evaprative cooling WILL work at 99% Relative Humidity, BUT... the key issue is that as the humidity goes UP the effeciency goes DOWN.

Also, another issue inside the Tucson homes is that the evaporated water vapor is DEPOSITED INSIDE the home, and thus contains the heat and that "builds up."

When you say the humidity is above 25% I suspect you are talking about the ambient OUTSIDE humidity. When that 25% air is drawn into the cooler, and evaporation and cooling DOES STILL occur, the humidity INSIDE the home MAY reach near 100%, and then there is no cooling.

I suspect that IF you open [just an inch or two] ALL WINDOWS in the house, then even at 25% outside humidity, the swamp cooler will be more effective.  By "venting" as much air as is taken in, you will hold the interior humidity down nearer the 25% mark and enhance the sensed cooling.

But even at high humidity [say 90% at 100 degrees F] a swamp cooler did work for years but the REALLY BIG PROBLEM was the enhanced high humidity INSIDE the houses cause EVERYTHING TO GROW A COAT OF MOLD/MILDEW.

When I was a kid over 60 years ago the swamp cooler was the ONLY air conditioning we had here.  Agreed that it wasn't perfect, but it was better than nothing I assure you.

Believe me as I speak from experience, evaporative cooling WILL WORK at high humidities.

variablechange (author)2011-07-18

How many gallons per hour does the bilge pump need to move? I imagine that a smaller pump would be plenty sufficient.

johnny3h (author)variablechange2011-08-21

The goal is to keep ALL of the padding constantly wet.  That does not require much circulation it the water outlets around the top of the pad are adequate in number, spacing, and size.

In the whole-house window unit swamp coolers I recall as a kid 60 years ago, the pump was nothing more than a CHEAP SUMP PUMP that people used to keep their basement sumps pumped out. They operated on 110-120 AC volts so they simply were attached to the wiring for the blower fan.

A small boat bilge pump should be adequate, but you would need a 12 volt DC power supply of the proper current [Amps] rating.

The issue is more having enough pump power to furnish enough head pressure to get the water up to the top. You can control the output by limiting the number and size of the output holes. You are right, you only need a trickle of water thru the pad. But it takes a sufficient pump to get it up there.

tiggerbob (author)2010-07-11

To use the evaporative cooler in more humid areas, one would need to dry out the incoming air. One way is to build a frame and attach heavy duty screen on both sides and fill the frame with water softener salt and set the frame in front of the cooler intake. when the salt gets too moist, set the frame out in the bright sun. It would be good to build two frames. One could be drying while the other is in use.

eranox (author)tiggerbob2011-08-01

That's a great idea! I was thinking about doing something similar, but on the output side, to ensure that I don't humidify my home to the point that I invite rust and mildew. I was wondering what I should use for a low-cost reusable desiccant.  This should fit the bill nicely!

If I ever get around to doing this (I'm thinking about one for the garage), I'll post some pics and let you know how it goes.

mwetzler (author)2011-07-26

where did you get your fan?

tooyellowdogs (author)mwetzler2011-07-28

it has been so long since I got the fan I can't remember exactly. Internet search solar supply or solar fan. That's how I found one. Sorry I can't remember the site. You may also want to see e-playa, a Burning Man chat site, under the subject: Cooling Your Tent or Van. for further detailed evolution of this idea, including sourcing updated materials. More great ideas there.

mwetzler (author)2011-07-23

nice shower; i want to camp with you!

joshcali (author)2011-07-09

Hey! about how many gallons a day does this use at burning man. Also, do you have/know inexpensive sources for cheap solar panels?

I'm really interested in this. love BM, but hate the heat. Would love a good RV alternative!

richardcole (author)2011-06-02

im not understand this whole project. from where it is look like cooler.... ???? tell me.

If I understand your question...the theory is to pull dry, hot air through a wet material. this causes evaporation of water which cools the air 20-30 degrees F. When this air blows on you via a fan, you are cooler. the lower the humidity of the outside air (hotter and dryer), the better it works. there are big,metal ones installed on top of homes and businesses in the Western US to cool the air inside. This project is made from recycled and easily obtainable materials.

Galileogst (author)2010-09-09

This is so awesome! My family and I hope to attend Burning Man next year, so I'm always on the lookout for ways to keep us comfortable in the extreme environment. I have not read all of the comments, so please forgive me if someone has already asked, but would you consider doing an instructable on how all of your burning man "home" items are made and used. Like the truck tent, the shower, your kitchen, etc. It's all so great looking and you did a wonderful job! Thanks for taking the time and energy to share. :)

tooyellowdogs (author)Galileogst2010-09-09

i'd be glad to help you. The truck tent is a Flip-Pac, they have a web site. Most other Burning Man related questions can be answered by searching e-playa, accessed from the Burning Man website. I have addressed our grey water disposal method (refined over 5 years) there, you can search for posts by author, look for Yellowdog. PM me at if you need.

Galileogst (author)tooyellowdogs2010-09-09

Thanks for the information! I'll check it out!

kenbob (author)2010-08-23

Excellent instructable. Now i just need a vacation someplace hot and dry to motivate me.

00MrNotWrong00 (author)2010-08-23

This is the coolest instuctable I've run across all year, thank you for posting.

sputnikII (author)2010-07-23

Forgot to mention a couple of things. Place hardware cloth (like chicken wire, smaller holes) over hole pad covers. Keeps out critters & gives support to pad. I used window screen but it's a bit restrictive and calcium deposits clog it a bit. Secondly, on the HOTTEST Mojave Desert days, my cooler uses 5-6 gallons of water. I know very well, because the 1st year I used it I filled it manually from gallon bottles ;) It runs 24 hrs. a day, you would too if you lived here. The pad on this is about 22" X 14". Just about right I think. Determined the size by looking at my buddies 1300 sq. ft. home that has the best swamp cooler I've ever seen. In here it's more like 130 sq. ft. Your water mileage may vary. To lighten the load on my $250 Fantastic Fan I bought an $18 box fan from Walmart and now use it as primary, kicking on the other when it really gets hot. Box fan is mounted outside, hung from roof, blowing outwards with air conditioner foam "sealing" it again a window, that just happened to be exactly the same size as box fan.

sputnikII (author)2010-07-23

I made one three years ago for my old Winnebago. There is a window in kitchen pointed right at dinette seating area, perfect. My Winnebago has a Fantastic Fan (brand name), quite excellent CFM, mounted in the roof. So the cooler has NO fan, depends upon the draw from that fan. It works excellent, I am in the Mojave Desert, it was 103 today, highest temp at my seating position was 89, not taking into account wind chill factor from the cool air blowing on me (NICE!). I made the box of plywood, cut large rectangular hole in back for airflow thru pad, square hole in front to same size as my window. Pad is laid over the back hole. On both vertical sides of pad are tiny eyelets, thru these I strung nylon string back and forth to hold the pad in place. Bought a submersible fountain pump and float valve. The float valve maintains about 1 gallon of water in bottom. Float valve is mounted on a steel framing "L" bracket.  Submersible pump sits in bottom, connected to plastic hose, which is run across the top of the pad.  Took a small nail and poked holes every couple of inches in plastic pipe, water seeps thru those, dripping down to constantly wet pad.  Entire inside is coated with Marine Varnish to waterproof. Hung from roof, meshed to window with airconditioner foam, voila! Fan evacuates hottest air at the roof (pushing air OUT), and cool air is drawn thru the pad, striking me. 3 yrs. and going strong. Oh, helps to adequately seal ALL openings everywhere, so that vacuum created by exiting hot air has no other intake source besides the cooler pad. Heck, gotta do that anyway if you don't like living with bugs. Do it, do it now!

spa31rky (author)2010-07-07

Terry Catlin The size of the duct work should be basically rated accordingly to the Fan supply. But here is an idea, ............say the fan / radiator is 20" and you want to use a 6" duct. All is needed is a Reducing hub. Basically make a reduction from the 20" down to the 6" that will also increase fan flow. Say the radiator is 20" square.........then you have to start out with a square flange and when reduced to 6" round. Get the picture?

nutsandbolts_64 (author)2010-05-14

 I wish I could build one here. My friend made one, but only worked for a while due to high humidity. If I do go to North America I will make one.

Jenn Nelson (author)2010-05-13

Very nice, and obviously playa-tested!   If I can get my vardo interior temp down from 105 degrees to 75 degrees using an inverter and batteries instead of my gennie, I'll be a happy camper!

CodySteed (author)2010-04-19

I used smaller sized materials and some other stuff last time.  I will be making a new rig this year, so I'll do a complementary instructable.

My materials:
Simlar set up as the above instructable, however the small pump and fan are solar.
Small Solar Fan
6 inch fan - 225 CFM which is pretty good for a tent and easy to put in a dryer vent exhaust tube.
Medium Sized, really simple to install in duct

Terry Catlin (author)2010-03-15

Gee, I wonder if that mysterious self sufficient Nevada festival  is the same one that I attend?  I'm not very handy but I'm purchasing a camper trailer for this year and just can't think of trying to catch a nap without some cooling. It will have solar panels on so that part is already taken care of but I have a few questions already.  The air 'tube' looks pretty big, could I get away with something smaller like a dryer vent tubing? 

The size of the tubing was predicated by the size of the car radiator fan used in the original design. Smaller diameter tubing would increase the air velocity, not a bad thing, depending on your needs. You could also try using a computer fan and a dryer vent hose. And yes, we're talking about sucessfuly  Burning Man tested.

rimar2000 (author)2009-12-01

For at least 30 years that I have been promising myself to build one of these, but since I had to design it from scratch, I always was postponed. Your design leaves me no excuses.

The disadvantage I have is that my area is very wet, and these devices require a dry environment.

NachoMahma (author)rimar20002009-12-01

.  Evap coolers are sometimes used in South Arkansas (US) to cool workers in plants and on work sites. It is very humid around here, but they still work, just not as well as in an arid climate.

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