Redneck Air Compressor Aftercooler

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Blog entry by PPK posted 03-20-2017 02:30 PM 4612 reads 1 time favorited 5 comments Add to Favorites Watch

I recently got a nice, used air compressor for a really great price. I have been needing one to power my air sander and also to keep up with my HVLP sprayer. This fits the bill perfectly. However, I want really dry air for using my spray gun, and also to make my other air tools last longer. Moist air isn’t good for any air tool that I’m aware of. So,
I researched a bit, and decided to make a cooling loop to cool the air off after it come out of the tank/compressor before it runs through my water/oil separator. Here are a few shots of it:

I used 1/2” copper tubing with flare fittings, and 1/2” threaded steel pipe & fittings. The concept is that the warm or hot air gets pumps up to the top, and then goes through about 37 feet of copper tubing coiled up, and cools down to make the water condense. Then the water gets caught in the drip leg, and the rest of it gets separated out in the water/oil separator. So far, I think it works. I got the compressor warmed up good, and the air coming out of the tank was pretty warm, and by the time it got to the water separator, it felt quite cool. The tubing on top was warm, and on the bottom was cool. I’ll have to test it out more this summer when the compressor gets hotter and the weather is moister, but so far it really seems to be helping….

Happy feast of St. Joseph, foster father of Jesus, a carpenter and patron of all fathers!

-- Pete

5 comments so far

View Bill_Steele's profile


723 posts in 2580 days

#1 posted 03-20-2017 04:05 PM

This is a great idea! I recently bought a small compressor for my garage (IR Garage Mate) and I also did some research on the after-cooler idea. I thought about buying a 1/2” copper wort chiller and maybe rigging that up somehow in a bucket of water. Your design is good because any moisture that condenses out should run down to the drip leg.

I wonder if an old automobile A/C condenser might also work? Are you getting more moisture in your water trap than before the after-cooler was installed?

Good job and thanks for sharing.

View Bobsboxes's profile


1447 posts in 3512 days

#2 posted 03-20-2017 06:27 PM

I like your set-up, I used just 1/2” copper pipe and fittings to build several vertical loops, with drains on the bottom of each loop. I no longer get any water in my water trap.

-- Bob in Montana. Kindness is the Language the blind can see and deaf can hear. - Mark Twain

View splintergroup's profile


3978 posts in 2070 days

#3 posted 03-20-2017 07:14 PM

Very effective!
Copper is gawd-awful expensive though. The A/C condenser idea is good, but there may be a tad more flow restriction then the copper tubing. Advantage is you can easily tuck it away with an electric radiator fan keeping the breeze going.

A common trick for instilling air lines is to have them slant (usually toward the compressor) so any water will collect where a drain valve is installed (bottom of the compressor tank).
A water separator is most effective at the far end of the air line after the air has had the most chance to cool off.

View robscastle's profile


7319 posts in 3052 days

#4 posted 03-22-2017 08:44 AM

Very good work, disguising your still as an air compressor!
Its even bad for wood as contaminants may effect finishes.
Dont forget to keep draining the pressure tank as water will still form in here.

Moist air is certainly bad for Air tools, so I hope you have an oiler own stream before the sander

The coils would appreciate you making a stability frame for them as well, to prevent movement and possible stress fractures.

Additional Information regarding Automotive coolers, the radiators and associated components in your car are designed to work at about 1 atmosphere above ambient, the output of a compressor can reach about 10x that so beware.

I am not sure of the pressures incountered in Transmission coolers or power steering systems.

If you decide to try this suggestion and I am not saying you should not… make sure you retain the radiator cap as its a safety valve for the system

-- Regards Rob

View PPK's profile


1790 posts in 1658 days

#5 posted 03-22-2017 04:35 PM

THanks guys. Yes, I do plan to do something to stabilize the coil a bit. I just haven’t thought of how yet. Perhaps a simple board with some holes in it and zip ties…

I also saw the wort chiller and thought of using it, but was told by my Mechanical engineer dad that a pressurized system like this should use flare fittings.

I’m really not fond of experimenting with any type of system that may not be able to handle air pressure, as I’ve heard about what can happen with exploding pressurized equipment. The larger the volume of air, the worse it is. So, I’ll stick with approved air lines, fittings & connections! I work for an industrial contractor, and we end up having to pneumatically test equipment and piping at times instead of the preferred hydro test. Lets suffice it to say that the entire area is cleared of people and locked out when the system is pressurized.

-- Pete

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