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stogie25 05-07-2007 08:07 AM

Onboard Misting System
4 Attachment(s)
For all of you that live in areas where humidity is somebody else's problem, evaporative cooling is a very good way of creating comfort. Here is a writeup I did on my latest upgrade for my Jeep.


Jeep Onboard Misting System

One of the primary reasons I bought my TJ ten years ago is because the lid comes off allowing me the open Colorado air all summer long. The flaw to this is that it gets hot in summer, sometimes uncomfortably hot. Usually when this happens I remind myself that the top will be on all winter, and that a little sweat is a small price to pay for the top being off. In summer I have always kept a misting spray bottle in the Jeep to spray myself when stopped at lights. If I thought running the air conditioner without a top or doors would do any good I would put one in. This year I decided to address the problem.

Among my favorite places to drive my Jeep to in summer are bars with patios. There I can enjoy a cold beer and the cool mist of the misting systems that many patios here have. It occurred to me that such a system could be mounted onboard a Jeep fairly cheaply. I researched this on the web, and found that it was not exactly an original idea. I even found a guy selling them pre-made. Unfortunately he was out of business. He is a very nice guy, and I spoke with him for a long time discussing the design of his onboard mist system.

His design pressurized a tank from a compressed air source, forcing water out of his tank at high pressure to misting nozzles. I drew up a design based on his using my 5 gallon Jerry can as a water source, and my onboard air as the propellant. After much discussion at work (bring up a project in a room full of engineers and much discussion will occur) we used a water pump instead of pressurizing the tank. It seemed quite a bit safer. We did however keep his approximate misting nozzle locations.

The project was adopted by the whole crew at work. One of the guys donated a RV water pump he had in his garage to my project. Another donated a slightly mangled garden misting system that he had laying around. We rigged up a proof of concept test, and made a wet mist mess in our shop in the middle of a very cold Colorado December. A little bit of mopping and the shop was good as new.

Just this week my top came off for the year, and work began on my misting system. The first day I did some shopping at my local hardware store for some adapters, ¼ inch hose to attach the misting nozzles, and a ½ inch feed hose. I mounted the pump behind my rear roll bar under the tonneau cover. I ran the ¼ inch output line up the roll bar, across my rear rack, and mounted the misting nozzles to the rack pointed at the cab of the Jeep. I drilled a hole for the feed hose, and a vent hole in the lid of my Jerry can, and ran the line down my roll bar to my pump.

The second day I installed a relay near my pump, and ran power from the battery. I ran a switch to my console to control the relay. With everything installed, it was time for an operational test. I filled my Jerry can with water, flipped the switch and made mist. I then took the Jeep out for a spin. Unfortunately it was 50 degrees that night, and the mist made the cab damp, and me cold, but it worked well.

The third day I worked out some bugs. It turned out the vent hole needed a small length of hose stuffed into it so the water didn’t jump out on turns and bumps. I also tried the misters when the temperature was in the low 70’s. The mist made me go from perfectly comfortable to cool, and evaporated almost instantly in the cab. I am waiting for a nice hot 90+ degree day to really test it out but my expectations are high. The aerodynamics of my Jeep are so bad that the mist is pulled from the rear of the Jeep to the cab at any speed above a full stop.

One benefit of the location of my misting nozzles is that with my tailgate open, I can turn the nozzles to point out the back of the Jeep. I can then put my folding chair behind the Jeep and stay cool when camping, or sitting in the pits at the race track.

Another benefit to developing this project at work was the advice I received from some friends of mine who are traffic patrol officers. In many areas, it is apparently against codes to carry modified gas cans, so it was suggested that I label the gas can “Water” to avoid being pulled over. I made a sticker appropriate to the advice.

Parts List
2 misting nozzles
1 RV water pump. 12V. 40psi.
1 relay
1 switch
14g wire
¼ inch ID hose
½ inch ID hose

Jerry can with feed hose
Attachment 31023

The hose running down the roll bar to the pump below
Attachment 31024

The pump mounted in the corner under the tonneau cover
Attachment 31025

The misting nozzles mounted on my Olympic rack
Attachment 31026

bruker 05-07-2007 08:11 AM

It's sort of like an onboard fire suppression system...:)

stevensinger 05-07-2007 08:20 AM

That is freaking awesome! Great JOB! While it does get hot here in NJ, i would just put my soft top back up and put the A/C on. I have a question, does the mist bother the radio and all?

stogie25 05-07-2007 08:32 AM

On my second test with temps in the mid 70's the mist evaporated almost instantly. I can't see myself running this under 85 degrees in normal circumstances. The mist should not harm any electronics if it is evaporating instantly.

Baotchi 05-07-2007 08:37 AM


I'd like to try that someday

jeeparoo 05-07-2007 09:01 AM

what a great system for you guys in non humid areas.. as for using A/C with the top and doors off, I do it quite often esp in slow traffic. Ill run it on the Bi-Level setting so it keeps my legs, arms, and face cool.. one thing id do is treat the water or use distilled water otherwise you will find the nozzles will clog up from tap water.

stogie25 05-07-2007 09:32 AM


Originally Posted by jeeparoo
one thing id do is treat the water or use distilled water otherwise you will find the nozzles will clog up from tap water.

I thought about that. I was picturing scum on the inside of my windshield vs. clogging up the nozzles, but they are both potential symptoms of the same root problem.

I used water that came through my Brita filter on my sink for the initial fillup. After it is hot enough to see how much water I go through in an average day I will see if I have to address that issue, or continue with my current method.

Bhelliom 05-07-2007 09:36 AM

Looks like a nice job. I've seen something similar in the past. And I guess its about that time of year to start thinking of stuff like that.

Up here in canada its usually already pretty humid. Wouldn't be as effective I dont think. If I lived down south where you are, I'd definitely think about something like that.

Dogman 05-07-2007 09:41 AM

Thanks for the write-up!

I played around with this last year (hand pump), but pulled it out because I didn't have the correct nozzles. It really makes a difference, especially for my boys. It hovers right around 100F most of the summer, so with no A/C, this is a nice addition.

LarrySchwegman 05-07-2007 11:44 AM

If you paint the can blue. It becomes a water can.

Nice system

neZZr 05-07-2007 01:10 PM

Not bad! I've seen expensive aftermarket setups, but I like the home-built setup even better. I might have put the nozzles on the front of the rack though, just so it isn't blocked when you have the rack loaded with stuff. :dunno:

Signalsoldier 05-07-2007 02:52 PM

Thanks for sharing this....

This would make for a damn good project this summer. What would you say the final tally would be now that you know what is required for the build. I mean if you did this for another jeep would you optimize anything or roll with the current config.

Rivka 05-07-2007 03:18 PM

fantastic idea and thank you for the good write up.
this has been a thought in the back of my head.
i would like to know what your water use ends up being as you use it more. I have a blue water jerry can i keep onboard in the summers, but would hate to think of running it dry since i have it for safety reasons on the heat as well, but getting it to do double duty would always be smart for a space confined jeep

stogie25 05-07-2007 03:32 PM

The expensive part is the pump. The Jerry can is not real cheap either. The rest is very inexpensive.

2 misting nozzles $10.00 at hardware store
1 RV water pump. 12V. 40psi. $130.00 from an RV shop
1 relay $5.00 from Radio Shack
1 switch $2.00 from Radio Shack
14g wire $400 from hardware store
loom $5.00 from auto parts store
¼ inch ID hose $6.00 from auto parts store
½ inch ID hose $5.00 from auto parts store
Jerry can $40.00

Signalsoldier 05-07-2007 03:49 PM

The good thing about modding is that its non-linear and as long as you plan properly it should work well.

I see with mounting in the rear like that is optimal for driving conditions but I was thinking it would be nice to have two jets near the front that would be just over the driver and ini So Cal the traffic can be a *****...maybe some sort of cutoff that you can divert the spray from front to rear with ease.

:dunno: let me put on my thinking cap.

The time now is 02:49 AM.

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