Emergency preparedness from a Counterintelligence Agent

DIY portable camping PVC pipe evap air conditioner

PVC swamp cooler 600x338Ok, so I saw the 5 gallon bucket air conditioner swamp cooler that figjam did a couple years ago and thought it was a fantastic idea. I wanted to see if I could improve on that. I finally got it. This is it, in my RV right now running off a car battery jumper until I hook it up to the 12V in the system.

This requires no ice, and will cool your RV or tent down at night while you’re sleeping.

All you need is water and a car battery to run this. Sounds like a perfect playa/prepper/camping project to me. I don’t like designs that require ice because you won’t always have it available.

A swamp cooler, or evap (evaporative) cooler works because it takes heat to evaporate water. That cools the system down. It’s EXACTLY the same thing as when you get out of the pool on a hot summer’s day and you get a chill. That water evaporates and pulls heat from your body just like it pulls heat from the air in this cooler design. It’s also the same science behind the Zeer pot I wrote about before that allows you to keep food or medicine cooler without using electricity. In fact, if you built a shelf in the middle of this system, it would cool food or medicine just the same as the coolgardie cooler I mention in that article.

If you think a swamp cooler won’t work, check out these temperature drops for different temps and humidity levels. You don’t have to be in a desert to use a swamp cooler:

evaporative cooler efficiency by temperature and humidity

But no, if you live in 90% humidity, OBVIOUSLY an evap cooler isn’t going to work very well. It’s still worth it if it drops your temps by 5-6 degrees though. Even in your home (where I keep mine most of the time), keeping my room cooler means I don’t have to run the a/c as high so I save electricity. In the desert where I live, it has the added bonus that my room isn’t so dry at night so it’s easier to sleep. Same thing in the RV.

To read the chart, find your current air temperature on the left (say 95 degrees) and your humidity (say 20%), this will then theoretically put out 74 degrees.

MAKE SURE you keep your room ventilated so it lets the humidity out. It might not make sense to open windows or keep the door opened a crack but if you don’t, it’ll get more and more humid in there, so your evap cooler will get less and less efficient. That’s the biggest issue with having the thing recirculate inside air as I have it at the moment. The last thing you want to do is have it run for hours and get it so humid that the walls heat up your room or tent faster than the cooler can cool it down. You’ll be sleeping in a swamp.

I spent several months dabbling here and there at different designs that involved large garbage cans, automobile air filters, and bunches of other stuff. I won’t bother to put all those failed proofs of concept here but I spent a lot of time and quite a bit of money on this project.

I checked the output of my system and it works fairly close to the chart. At 79 degrees in my bedroom and 10% humidity outside (higher inside but I didn’t have anything to measure it inside but I’ll update this post as I do more testing), I was getting 63 degrees coming out of the fan at the top. It had no problem cooling down my bedroom after a few hours, and I have a very large bedroom.

Figjam’s original 5 gallon bucket air conditioner

First, my design is going to be a bit different but that doesn’t take anything away from Figjam’s. His has some advantages over mine but it just wouldn’t work for me.

If you’ve already read my previous article on the 5 gallon bucket air conditioner, you can skip down about a quarter way through the article where the line break is and find Start Here

Figjam’s idea puts out about 150 cubic feet per minute and uses about a gallon every 2.5 hours or so. It requires about 1.6 amps for the fan and has a pump that should supply its own power.

He uses this pump, which has its own solar panel with it, which puts out 42 gals per hour. It has its own solar panel with it.

His framework is a 5 gallon bucket from Home Depot, which is super cheap.

He uses a Dura-Cool evap cooler pad, which is a great pad for this type of project.

His fan is a Delta AFB1212SHE 120mm x 38mm Very High Speed Fan. It puts out about 150 cfm and takes 1.6 amps.


About my higher volume portable evap air conditioner

I wanted to change things a bit to make something different. I found the bucket cooler wasn’t quite enough to cool my RV but it was putting out cool air, so I needed something bigger. Here were my requirements:

  • At least 500 cubic feet per minute output
  • Under 3 amp current
  • Runs completely off 12V
  • Not too expensive
  • Very portable (A similar size to a 5 gallon bucket and light enough to carry easily)
  • Very simple to put together, even if you don’t have a lot of mechanical ability

Because I needed more airflow, I needed a bigger fan. I did a lot of searching and came up with a great one. I had the damnedest time keeping it all cheap, easy, small, and efficient but it’s all that now.

My plan uses an Fan-Tastic Vent Endless Breeze 12V Fan. It puts out a whopping 900 cubic feet per minute (which is 6x what the computer fan does) and has fantastic reviews on every camping site that I looked at. It also runs off 12 volts and amp, 1.5 amps, and 2.6 amps for the 3 speeds that it has. I like that it has 3 speeds because I can crank it up if I want to (which is a lot of air) or put it on low and conserve battery power if I need to, depending on which source I’m using. I had considered just running a larger computer fan but for the money and for the cfm you get per amp it takes, this is much better.


Because I’m using such a large fan, I needed to have a LOT more intake capability than the 10 holes in a 5 gallon bucket allowed. I estimated that he was using 4″ holes, so pi*rad^2 = 12.5 sq inches each = 125 sq inches. Since my fan puts out 6 times the airflow that Figjam’s does, I needed at least 6 times the filter area.

I came up with this frame. It’s 30″ high (about the same as the bucket with intake pipes) and 15″ square at the base and top:

swamp cooler frame

My intake is approx 12″x24″x4=1152 minus 4″ of water (assuming the tub is filled to 5 inches) = about 960 sq inches of intake: 7.7 times what the bucket can pull in. As you fill the tub higher, it covers more of the filter so there’s less it can pull, and the opposite for when the water level drops.

Because it’s made up of a 1/2″ PVC frame, it’s very light and can be torn down in just a couple minutes to fit into the tub.

I wanted a little more water flow than the original design but I didn’t need it to be too much bigger because the original piping at the top where the water comes out was about 8″ in diameter or about 28″ of holes. Mine is about 48″ inches of holes. To be optimal, you just need enough water so the whole pad stays wet on full. Any more than that just moves more water (which has a slight cooling effect in itself) but doesn’t cool the air much more at all and costs more power.

I ended up going with the KEEDOX® DC30A-1230 12V Phase CPU Cooling Car Brushless Water Pump. It puts out about 64 gallons per minute and uses about a third of an amp. It’s also super quiet, unlike the 120VAC pump I used from a water feature when I was figuring out how to design the thing. I works pretty well and fills all the holes with water at the top. If you pull the pad tight and adjust it as necessary when you set it up, it keeps the whole pad wet.

Start here

How to build the PVC evap air conditioner

Evap cooler parts list

So here’s the meat and potatoes of what you need to do to build this evap cooler.

  • 2 10′ sections of 1/2″ pvc pipe. This will be mostly cut into (18) 13″ sections with one of them cut in the middle again. You don’t have to do this exactly but this gives you just the right amount for using two 30″x36″ evap cooler pads without having to cut them down to size. If you use a different size, just adjust accordingly. Home Depot and Lowes carry these in 10′ sections. Might want to pick up one extra in case you mess up because they’re super cheap. You can just get a bunch of 12″ or 24″ ones if you want but it’s a lot cheaper if you get 10′ ones.
  • 8 1/2″ PVC 90 degree Elbow connectors. These go on the top and bottom corners.
  • 4 rubber stoppers to keep water in the top part of the pipes.
  • 4 1/2″ PVC Tee connectors. These go in the middle for the two cross pipes that add stability.
  • 1 1/2″ Tee with thread to thread in the nozzle where the hose will connect in the pipes.
  • 1 90 degree PVC to hose barb connector to connect the hose to the threaded Tee.
  • Fan-Tastic Vent Endless Breeze 12V Fan.
  • 1  KEEDOX® DC30A-1230 12V Phase CPU Cooling Car Brushless Water Pump.
  • Any way you want to connect the two wires from the water pump into your battery. You could connect a 12v connector so it plugs into a cigarette lighter like the fan does or you could put clamps on it like I have temporarily.
  • 2 30″x36″ Dura-Cool evap cooler pads.
  • A couple feet of cheap 1/2″ hose (the blue hose in the images).
  • A short amount of 5/16″ inner diameter/ 7/16″ outer diameter hose to connect between the water pump and the 1/2″ hose.
  • A small hose clamp to fit the 1/2″ hose over the 7/16″ hose so it doesn’t leak.
  • Roll of bailing wire to cut into sections a few inches long to poke through the padding and keep it in place. It gets rusty but it’s what I’m using for now because it’s super cheap and can be reused when I disassemble the unit.
  • A container to put it in. I’m using a 71 qt Rubbermaid that I got from Home Depot but Amazon also carries it and other sizes if you don’t want this exact one.

Tools needed:

  • Hacksaw to cut the PVC pipe
  • Flat screwdriver to tighten the hose clamp
  • Pair of scissors
  • Whatever electronic tools you need to connect the two wires from the water pump into your 12v supply

How to put the PVC swamp cooler together

First, cut your PVC pipe into eighteen pieces, each 13″ long. Make a square with those four pipes and four of the elbow connectors and make sure the fan will sit on top without falling through.

Cut one of those into two pieces and cut an inch of one of those so the total is 12″. Doesn’t matter exactly where but it should be at least a few inches from one of the ends. Your hose Tee will go in the middle of these two. See the full layout pic a couple of images below and you’ll see it.

Take four of those pipes and drill 1/16″ or a little bigger holes, about a half inch apart. This doesn’t have to be exact and you can change the size of the holes and spacing, but they must be in a line parallel with the pipe or some of them won’t fill. If your holes are too big the closer ones will drain out before the farther ones get water. If they’re too small, you’ll most likely just have water shoot out a couple inches which isn’t a problem. If they’re really too small, it’ll back up your pump or start leaking out between your PVC sections.


PVC pipe with holes


Make another square with four other 13″ pipes and four elbow connectors.

Here are all the PVC framework pieces all laid out:

swamp cooler PVC framework pieces laid out

Take your base square and put in four of your 13″ PVC pipes in the holes:

PVC base with four posts

Take two 13″ PVC pipes and place a 1/2″ Tee on each end. Put these on top of the four posts you just added. Doesn’t matter which posts:

PVC with cross beams

Put three 13″ pipes onto the top of the holes in the cross beam pipes as well as one of the short pipes that you cut. Put a stopper in each of these at the top. The stopper isn’t critical, and you can just stretch out a plastic bag at the top as you fit the next piece and rip off the excess if you want. The stoppers just keep the entire framework from filling with water, which isn’t really a problem but uses up some of your water to fill the pipes that won’t be able to be used by the system.

Upper posts with stoppers

Put the threaded Tee on the top of the short pipe.

Put the other part of the cut pipe into the top of the threaded Tee. The total height of that part should be the same as the other three legs.

Thread the hose bib into the threaded Tee.

Threaded Tee and hose bib added

Place the top square (the one with the pipes with holes) onto the top. Adjust the holes so they all face in and a little bit above the center of the pipe:

swamp cooler frame

You’ve now completed the framework.

For the next part, you need to connect the water pump to the hoses and the hoses to the PVC pipe. Here are the pieces laid out:

water pump with two hoses and clamp

The water pump takes a 5/16″ inner diameter hose and the PVC hose bib takes a 1/2″ hose. If you slide the blue hose over the clear one and tighten it with the hose clamp, it won’t leak. If you use a water pump with a 1/2″ bib or find a bib that works with the smaller hose, you can connect to the PVC Tee, you won’t need to do this.

Place the blue 1/2″ hose into the PVC bib and let it drop to the ground. It’ll probably be curved so make the curve go toward the middle so it ends up pointing out near the closest corner so the pump is pushed that direction.

Place the water pump with whatever length of clear hose you want and cut the blue 1/2″ so it fits over it. When it’s done, it should look something like this but the big thing is to make sure the water pump will stay at the bottom and under water. The nice thing about this particular pump is that the inlet is on the side and not the top like some of them are so you don’t have to have the water as deep:

water pump and two hoses connected to PVC tee bib

You need to connect your two wires from the water pump to some kind of connector.

Now it’s ready for testing. Put the system you have so far into a tub of water and connect the water pump to 12V. You can use one of these 12V Fused Replacement Cigarette Lighter Plugs with Leads if you want to connect it into a 12V receptacle, use clip-ons like I have at the moment, or whatever else you want that will connect to whatever 12V supply you’re going to use.

When it’s running, check that all the holes have water coming out. They may not shoot out but it’s definitely fine if they do.

water coming out of PVC pipe holes

Now for the fun part. You should have two evap cooler pads. They are 36″ long and the tower is 30″ tall. That gives you 3″ on each side to wrap around the pipe from the inside to the outside.

Place the pad inside the tower and center it (make sure the long way of the pad is with the long length of the tower or you won’t have any overhang. Cut the center of the pad with scissors down a few inches right in the middle where the corner is, on the top and the bottom so you can wrap the top and bottom halves over the pipe without having to stretch it in the center.

evap cooler pad with cuts

Place one edge at the PVC Tee hose bib as shown. This will ensure that you don’t bulge out the center of the padding and your wiring for the pump can exit right where the pump is:

Pad placement in tower

Cut off several 3″-4″ sections of bailing wire and fold them like large staples. Fold the top of the padding over the pipe and back down on itself a few inches below and poke the bailing wire into the padding to keep it in place. Do the same for the bottom. It should be pretty snug. This is a view of the center corner, from the inside.

padding with bailing wireHere’s what it looks like when it’s pretty much padded in. You’ll be making a few adjustments once you get water running in it in a few minutes:

Full frame with padding

Place the tower and padding back in the tub and turn on the pump. You should see water coming down all sides. Here’s where you make adjustments. Wherever you see water dripping down instead of flowing through the padding, you need to add some bailing wire to tighten that section. You also need to make sure that you don’t have any gap between the pads or air will go through there instead of your padding. Make sure the entire padding is getting wet.

wet evap cooler pad

Once you’ve done all that, all you have to do is put the fan on top and you’re done! Just put it in whatever container you’ll be using and fill it with 5″-6″ or so of water and you’re ready to feel it blow out some cool water. Here’s the tub I’m using but you don’t need to use this one as long as you get something that’s at least 15″ wide on the inside at the bottom and not too big:



If your water is warm when you start, it’ll take longer to get cool but it’ll eventually work. You should have some kind of ventilation in your tent or RV to bring in dry air. You may even want to do something like wrap it in a large plastic bag around it all except the fan and poke a hole for air to come in from the inside through a dryer hose.

PVC 12v evap swamp cooler air conditioner

If you notice, I have a float hanging off the back of the container to the outside. That’s a swamp cooler float that allows the water to fill up to a certain point and then automatically stop. It works but it leaks at the moment so I need to put some goop stuff on it to get it to stop. Once I get it to work flawlessly like the swamp cooler, I’ll post the details of it too.

BTW, if you’d like to see more DIY articles, check out these I’ve written:

Make fresh homemade butter with heavy cream and a mason jar

Eat healthier by becoming your own grocery store

A simple way to make your own char cloth

How to make your own DIY hand pump

Keep your food cool without electricity: Zeer pots

How to run your electronics on dead batteries: the joule thief

Using solar to cook: DIY solar oven

How to make a datoka fire hole

Free hot water forever DIY project

Simple DIY portable solar power unit for camping or emergencies

Build your own DIY 5 gallon bucket no-ice evap air conditioner

Please share this article with anyone who camps or might want a way to cool down an RV or even a bug out shelter – or who just likes to build cool DIY projects.


About graywolfsurvival.com

I am a former federal agent and military veteran who has deployed to combat theaters in Africa, Iraq and Afghanistan and have almost three decades of military and military contracting experience.

My goal is to help families to understand how to intelligently protect their family and their way of life against real threats, without all the end-of-the-world doomsday crap.


  1. This plays on the classic Arabian idea of hanging a wet blanket at the entrance of a tent, so when the air blows in it cools the tent.. I’m interested in something that doesn’t increase the humidity, such as for cooling a space where humidity would be a problem like for a station with electronics..

    • graywolfsurvival says

      You’d need to expand and contract some kind of liquid that has exothermic and endothermic properties in order to do that. Much more complicated. Other than that, the only way really might be to dig deep and pull the air through the ground underneath to cool it down.

  2. graywolfsurvival says

    That design is called a zeer pot – https://graywolfsurvival.com/2874/keep-food-cool-without-power-zeer-pots/

    I’ve seen somewhere that a guy was keeping his horse stables cool with a wall that did that. It’s actually where I got the idea to do these articles on evap cooling.

  3. ethan stewart says

    this is a pretty rad design!! any recommended tweaks if you are making a plug-in version?

    • graywolfsurvival says

      I think if I were making a plug-in version I’d just make it bigger, but not by much. The problem is that the taller you go, the harder it is to keep the mats straight so the water doesn’t skip over parts. That fan is pretty awesome but if you’re going ac, you might be able to find one a little less expensive but this one really gives you a great fan for the money.

  4. Instead of keeping a window open or the door cracked in a camper, maybe you could use a dryer vent with a RaspberryPI monitoring the humidity inside the camper. if the humidity exceeds your threshold, it turns on a fan that vents to the exterior. I think a raspberryPI has extremely low power requirements. As a bonus, when the vent fan isn’t running, the dryer vent flaps would be closed keeping hot air from coming making its way inside.

  5. I’ve been working on converting my van to be able to live in it recently and this would be perfect! I have a few ideas/questions:

    Do you think it would be possible to combine this with a zeer pot somehow? Perhaps put the zeer pot above the fan to increase air flow/evaporation inside?

    Or is there a way to put shelves and/or food within the air conditioner?

    Alternatively, I’ll have a fantastic built into the roof already to remove heat/moisture – can you see any way to turn this into an evaporative air conditioner? Or would that just bring all the cold air outside?


    • This is essentially a zeer pot on steroids.

      The coolgardie safe does this with food inside: http://en.wikipedia.org/wiki/Coolgardie_safe

      We use large versions of these on LOTS of homes here in AZ.

    • James Palmer says

      They make 12v roof mounted swamp coolers for RVs. They look just like the AC units on the outside, but they are 12v swamp coolers. They are not cheap though. I did a simple Google Search for 12v swamp cooler and found them Fire around 650 bucks. I am going to build one like this, except I’m going to enclose it all in with some kind of box and mount it so it works and looks more like a traditional window mounted swamp cooler. My rv is in a fairly permanent spot, so I can stand a little more rigid installation.

  6. Pretty great idea. I actually built something similar to this quite a few years ago, but for a little different purpose. I had completely forgotten about it. Your plan is greatly improved over what I did.

    I do have one observation, with a question: From the photos, it appears you ran your test in your bathtub/shower. So, is that Mr. Bubble bubblebath up on the shelf in the shower?

  7. Neat design. I’m going to go with it as the base of my build. I’m thinking of making two modifications…

    1) I’m going to put the pads on the outside of the tubes. Then I can hold them on by wrapping straps with velcro around them to hold them on, making it easier to tear down the unit, and also providing a bit more surface area.

    2) I’m going to have the fan blowing out, and into a piece of ducting (http://www.amazon.com/Plenum-Ceiling-Round-Connects-Register-Diffuser/dp/B00B0648ZG) that goes around the fan and adapts the square fan shape to a 10″ round flange. Then I’ll put the unit outside my camper, and run 10″ duct to an insert in one of the sliding windows of my camper.

    I have a small popup camper, so I don’t have room for this unit inside, and it will work better outside in the dry air.

    Anyone see a reason this won’t work?

  8. This is truly great, very impressive and useful.
    I’m considering installing a poptop roof in my campervan and thinking about how a diy evap cooling setup in the pop top might work. It looks like it would be fairly tricky to come up with a design that can fold into the roof but possible maybe, will post here if it comes together!

  9. We also camp in a primitive area and this would be so useful your design looks awesome I really appreciate you posting it.
    Unfortunately the company vehicle does not have air condition provided I can get quite hot here in Texas while delivering mail all day. Do you think a smaller compact version of this could be made to fit in the delivery vehicle without ruining paper goods? The windows are often open and i get quite a bit of ventilation but it would be nice to have some cooler air blowing just for personal use, something that could easily be taken in and out of the vehicle on a daily basis.

    • I don’t think it’d add so much humidity to your vehicle that it’d ruin paper goods since you’ll be opening the doors so often not a lot of humidity can build up but no way to know that without trying it.

  10. Thanks for sharing this! I just built one (in time for San Francisco summer, which comes in October and April). The only improvements I could suggest are using fishing line instead of baling wire bc it won’t rust, and I wired my water pump into my fan (drilled a hole into the plastic case for the wires to go in).

  11. I’m a little late to the party, but I was wondering, it looks like it has 2 plugs, is there any way to make it just one? My RV only has 1 12v plug. Sigh. I’m planning on installing some in the living room area, but in case I don’t get to it…..

  12. Sandy Patterson says

    Just throwing this out there, since I haven’t built one yet, and am not conversant with the materials. Do you think that by basically turning your design on it’s side, so that the long side was the base, you could achieve more capillary action to wet the bottom, meaning less need of pumped water and helping to reduce the pump power draw? Also, since most of the pipe is structural, not functional, why not zip tie a couple of milk crates together for the framework? Might provide more lash points for the material, lower cost, and have greater rigidity. Last thing, just a quick heads up; you’ve got the Keedox down as 64 gpM in your tech order. Website says ~=64 gpH (4L/m).

  13. Great design but I think it would be a little tidier to use zip ties instead of baling wire, no rust.

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