I'll be painting sometime soon and recently there has been several timely paint related threads. In the Midwest we're plagued by humid weather and lots of water in our compressed air. I figured I'd share my project to rid myself of water so my paint job isn't ruined.

There are several high dollar units out there to separate water from the air but I'm cheap. I decided to design some piping meant to drop the water out of suspension. All you need is 25' or more of piping, some valves, fittings and good old gravity. I wanted to use copper but it would have cost me over $150 in materials. Going with PVC cost me $40.

I still need to finish the drain and inlet/outlet piping but you'll get the idea.

That workers very well. Btdt. If you double the pipe size going up and down vs your other drops, the air moves slower as well and helps.

The risers I have are 3/4" with 1/2" on the inlet, outlet and drain. In hindsight I suppose I could have gone with 1" and it would work even better like you said. One issue is as the piping size goes up the pressure rating goes down. I think 1" is rated for 160 psi whereas the 3/4 is over 400 psi and the 1/2 is 600 psi. My compressor is set at 145 psi and close to the 1" rating.

One other thing that can be looked at is schedule 80 pvc .. its usually grey but the pressure rating is a lot higher ..also for the others looking to do this be aware that there is different pvc white pipe some are very thin wall and low psi others thicker .. read the little print that is on the pipe itself ...

Be very careful!

If a PVC water pipe bursts under those pressures, no big deal, it causes a leak.

If a PVC pipe bursts under AIR PRESSURE, it can come completely apart and throw shards around the shop.
The difference is that water is incompressible while air is compressible.

You have a LOT more energy stored in a compressed air system than you have in a water system at the same pressure.

I would use that with caution and bleed it every time you are not using it.

Stu

I looked into this awhile back as well, and my take away was that a copper, or steel lines transfered the heat out the best, and allowed for improved separation. A few guys were even plumbing lines through ice buckets or chests to get things cooled again, I don't know how successful they were though. You probably know that you want a flex(hose) connection between the pvc and compressor given the vibration and heat at this connection point. I'm going to be needing to do this as well some day, so I hope you get good results that we can learn from.

That 3/4 piping is rated at over 400 psi of water. It's well within it's limits at 145 psi. It's true that air will have more volume for a given pressure.

Look at all of the shop air DIY kits out there. They are thin walled plastic pipe rated under 200 psi. I haven't heard of a catastrophic failure yet that threw plastic shards everwhere and hurt someone. Show me one of those and I'll re-think my setup.

The shop air diy is not hard PVC.. I have had PVC pipe blow up on me at a shop, cheap shop owner put the thin wall PVC in and wow. That shit sounds like a bomb going off. hurts like a son of bitch to!

It works, just watch sharp blows or flexing.

Just a thought.
I used all black pipe in my first shop.

This one I'm renting now. So I ran the overheads in PVC. But all the down pipes that are at the area that a human could come in contact or be in harms way I converted to steel.

Works pretty good.

Actually I had the same PVC in my shop with 6 guys working full tilt all day for 18 years. We had about 6 blow outs in that amount of time. Shards fly everyplace and shock the entire line sometimes causing a break down line. It's pretty safe but it can break.

I'm surprised this stuff shatters apart when it breaks. Figured it would just split. Can't argue with experience.

I gotta say I knew a bunch of folks would have issue with it. Some people just don't like PVC even when the pressure rating is clearly printed on it. I also had my doubts and built my house with copper water lines. I suppose I'll find out if the rating is accurate.

On a side note. I've seen plenty of rubber air hoses break. Had to fix an aircraft skin after a hose end broke, whipped around and smacked it 150 times before the air got shut off. I also saw a guy get slapped silly inside a cargo bay when the hose end broke. Now that one was kinda funny but scary at the same time. Strange that no one mentions the rubber hose.

""It is recognized that while adequacy of strength is an important element in the safety of a compressed gas piping system, consideration must also be given to the nature of failure should accidental failure occur, whatever its cause. Above-ground piping which fails by shattering can present a serious hazard to personnel by the resultant flying shards, or pipe fragments, which are rapidly propelled by the released energy of the suddenly decompressing gas."

http://www.lni.wa.gov/Safety/Basics/HazAlerts/902.asp

It is the "nature of failure" that is the issue.
Steel or copper just leaks.... PVC explodes.

Stu

I worked with a guy that had a scar on his head from a pvc pipe that shattered with air but I don't remember what generated the break. That said I have PVC in my shop with about 12 outlets but I was careful how I did it. All PVC is covered with sheetrock and terminates in black pipe. The black pipe is attached to the studs with a metal bracket so when you pull on the line you are NOT pulling on the plastic. 20 years that way with no problems. If you use big impact guns, don't go too small.

If I had a small shop I would run copper but who can afford that these days?

Besides the argument PVC vs copper or steel, the theory of dehumidifying the air is simple. A compressed gas gains heat thru compression. A condenser, fin and tubes, or mechanical, cools the compressed gas condenses the moisture back to a liquid, provided the dew point of the H2o is achieved. Some air driers require a refrigerated condenser to hit that dew point. Then separate the two with a trap. Simple as that....
The PVC is a safety concern but mostly a poor heat exchanger. look for an old AC condenser at the local junk yard, size the piping to avoid a pressure drop. run some sort of fan in front of it to cool the hot gas, a water trap on the outlet and viola, you should be good to go. It is best to install this on the compressor discharge line before entering the tank. Then a second trap exiting the tank. Graingers should have H2O traps fairly cheap.
32 years in the refrigeration industry I condense gas, and exchange heat several times a day

I have a confession to make.
My compressor is an oil-less 30gal Craftsman kinda' like the one in your pic.
I also looked into the prices of air driers....not traps, driers. Uh oh......DIY is supposed to be cheep.

Being a hammer mechanic, I drained the water from my tank and went for it. I also shot it (both primers & top coat) when it was humid (normal for the NW bout 50-70%) and cooler...... about 55-60 deg.

I had no problems with water in the gun or in the paints.....the paint is still on 7 years later.....still a 10 footer tho.
Yeah, I violated every painting rule I ever read about..... I'd rather be lucky than good.

Sort of begs the question: Do vertical runs: work? Better than nothing? Not at all?

I've sprayed with a $100 "separator" with mixed results. Don't know exactly what moisture does to paint but on hot/humid days I've had blush and had to re-do a few times.

The biggest thing outside of pipe selection is again moisture.

The longer the runs, the better the ability of your 1st water separator to knock out moisture. Vertical height of 6' is a good minimum. 30% moisture drop is a good minimum after the 1st separator - And, I pulled that number outta my ass

The higher the air consumption, the cooler the circuit runs. That's why home units tend to have more moisture in them. Keep your tools oiled daily... Always use disposable inline driers for paint guns if you can afford it, if not, keep a cookie sheet close to redry the huge amount of beads if using that method.

Good Luck...

John,
As a supplement to your system, I have a big desiccant dryer I bought at Harbor Freight a few years back. I used it as a stand-alone drying system and it worked great. It's a large steel tube about about 2" ID x 36" long. Air enters the bottom travels up through the desiccant material and out through the top. Between gravity and the desiccant it is very effective. I have 1/2" fittings on it so it won't reduce airflow downstream. I can no longer find one on the HF website, but you are welcome to borrow mine. I'm in LaGrange, but can arrange to get it as far as Gurnee where a friend of mine would be happy to hold it for you. PM me if you are interested.

Funny you should mention that. I was there today to buy a furniture dolly and saw it. I had it in my hands even but couldn't decide whether or not to buy that one or the small inline one. I decided to wait and didn't buy either. I really appreciate the offer but I'm lucky enough to have a HF just down the block.

I stumbled onto one of those HF driers on the close out shelf at our local HF about 6 months ago. I actually just installed it about 2 weeks ago. I also have a Motor Gaurd filter on a branch of the sir line I only use when painting. It has a large toilet paper roll filter. The one draw back with the Motor Gaurd is the thing corrodes when it sits with a wet filter. I actually had one corrode through and blow a hole. Luckily my son stopped over before my compressor went into melt down. The one pictured also started to corrode inside. I ended up cleaning it out and painting the inside with POR15.

You should get the big one. And soon. It's not listed in their online catolog that I could find. I think it's discontinued. I got two bags of pellets with mine. the tube takes one to fill it. That means you can dry one bag and fill it with another.

They only had one. I can't make it there tomorrow. I'll have to hope it's still there on Wed.