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Air compressor water trap

5.7 hemi

FBBO Gold Member
FBBO Gold Member
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2:56 PM
Dec 21, 2008
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So what are you guys using to keep the water out of your air lines?
I have two in-line filters.
Also, i have a kit I purchased with my Quincy compressor, it uses a roll of toilet paper and has drain set-up.
But, I have not installed it yet.
I use 3 water traps. One down-leg from the main line coming from the compressor, and one running down at each of the two manifolds I have set up (1 oil-free for paint, media, ect.. 1 with auto oiler for air tools)

Both the oil free and oiled manifold I run Ingersoll Rand Air/Water/Oil separators. Side for the air tools I obviously run the Auto-oil unit after the separator. Paint/Media side I also run a Devilbiss desiccant canister/filter. I'll typically run a twist on Whirlwind air/water at the gun as well. System works well. No issues with Air tools rusting inside or moisture in the media/paint. On real humid days I run a desiccant snake along with everything else, on the paint/media/blast side.

Hope it helps
I use the Husky 3/8. Definitely not the best but as of right now I only use it for air tools, and that's mostly air ratchets for lug nuts. I will upgrade for sure down the road but I was trying to keep it cheap. I think I spent $30-5.

Sure would be nice to have a system that dried the air before it made it into the tank. The water that comes out of my compressor is pretty nasty.
Sure would be nice to have a system that dried the air before it made it into the tank. The water that comes out of my compressor is pretty nasty.

You'll need an aftercooler for that, it's pretty hard to dry out hot air. Once it's cooled down you can pull the water then run to the tank. That's a lot more plumbing plus wiring for the cooling fan.

Although I suppose you could rig up a few feet of pipe within pipe and surround your air line with a larger water pipe, running cold water to a drain as it collects the heat.
In addition to the in-line filter may I suggest the use of an automatic tank drain. They keep water from pooling in the tank sump and should cut down on corrosion. About $15 @ Harbor Freight.
I plumbed a transmission cooler into the output of the pump before the tank. There is a fan that runs with the compressor attached to it. A down leg catches the condensation before it goes up and into the tank. It does a wonderful job of eliminating moisture before the tank. I have a thread on it around here somewhere. Then I have a vapor separator (that doesn't have to do anything) and a Motorguard filter on the output.

Here's the thread.
That was the thread I've been searching for dpstark2!!!! Hope ya don't mind if I steal that brilliant idea and use the crap of it!!!! I have 3 water traps and still get moisture/water in the line. I'll post a pic of my set up so all can see what I've done and maybe get some advice.
Steal away! I stole (eh, well, he offered) the idea from a friend. A good compressor is a big investment, and I want that tank to LAST!

By the way, I never get water at my tools or the spray gun. The vapor separator drips once or twice after a hard day's use. That's it.
I have found a nice trans cooler and will use that, but I'm gonna take it a step further. Once out of the cooler, copper line down to another tank (5 gallon or so) then back up to the compressor. Water will hold in the smaller tank and with my water trap directly off the compressor outlet, I should in theory, be water free.
Just a couple points to consider, in case you haven't. That second tank needs to hold up to the peak output pressure of the pump, which will be higher than the main tank. Second, if you have "head unloaders," you'll want to move the one from the main tank to the input of second tank, or that whole 5 gallon tank will hiss forever every time the pump stops. In this case, the 5 gallon tank should only see the main tank pressure.

I have another tank I was going to convert to a desiccant tank after the main tank output. I haven't gotten to it, but the same can be accomplished with a few lengths of parallel 2-3" pipe.

If you get really creative, you can wire in a time delay relay and automatic drain to bleed off the water from the bottom of either (or both) tanks automatically. I've never bothered- my 4' water collection tube fills less than a foot deep after a day on the D/A, so it's easy enough to drain.

Post some pics when you're done!
I had water coming out on mine when I originally had the trap/filter attached right at the line out of the tank. I added a 25' blue slinky hose at the tank before the trap/filter. My yellow work hose plugs in at the trap/filter but there's now 25' of "cool down" hose before it. That made it stop letting water thru, because the air is cooler and the water separates from cooler air easier. This was a low-buck, quick, and easy fix for me. Other's results may vary.


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I actually bought an ac condenser (automotive) and also got a huge water trap/filter. Waiting for the ac condenser to arrive, but the large and in charge, lol, filter/water trap is working out just fine for now.

What is a "head unloader"?
My A-Compressor is fairly small but should have a water trap on it, something ive thought about a few times and even my media blaster has one and it does collect a small amount of water, ive never had any issues with water on what ive painted with mine but i do use in line water filters so maybe that helps, at least so far. They are a good thing to have...
A head unloader is a valve attached to the tank at the inlet that senses when the compressor shuts down and bleeds off pressure in the line between the compressor head and the tank. It increases the life of the valves in the head. If your compressor hisses when the pump turns off, you have one. If not, you don't. In my setup, the cooler and extra lines took the hiss from 1-2s to about 15s. It's not bothersome, but if you had one on your main tank and added a tank between the pump and main tank, you'd bleed off all pressure in the secondary tank when the pump shut down.
I'm running a Hankinson refrigerated air dryer after my compressor, 2 stages of filtration ahead of the dryer.

From there I feed 3 lines, 2 are basic shop air lines, one of which feeds my blast cabinet. The third line goes to my paint booth, and has 4 stages of filtration prior to my regulator in the booth (ridiculous, I know).

But I really, really hate contamination issues considering the amount of time that I have invested in body work and prep prior to paint.
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