Compressor plumbing and accessories

[Deleted member 12521]

Hi All,

I've got a two-stage, 60 gallon, 5 hp compressor, which I'll be using for air tools, sandblasting and painting. I'm new to this hobby, and from what I've read water and other contaminants can ruin your tools, cause your sandblaster to clog and no end of problems laying down paint.

My current plan is to run some air line (black pipe or copper, the relative coolness of which which I understand will cause some of the moisture in the air to condense and be able to be removed at an appropriately-located drain) up the wall from the corner where the compressor is located, into the attic and back out the ceiling in the centre of the shop where I'll mount a retractable 50' reel of 3/8 PVC hose. I don't need individual hookups all over the shop (I find using a retractable extension cord that I've similarly mounted near the centre of the ceiling to be very convenient. I plug into that more often than any wall outlets). I'm not sure what diameter pipe to use. 1/4"? 1/2"?

I also plan on putting a desiccant filter and a coalescing filter in between the pipe and PVC hose. I've seen some with 3/8 fittings and others with 1/4. SCFM ratings also vary. I'm not sure what will work best for the intended uses.

Any and all advice, suggestions or experiences welcome and appreciated.

 

[TR3driver]

I had a lot of trouble with water when I was running a little 20 gallon unit in the garage; but it has been no trouble at all with the new arrangement. Got really tired of listening to the noise, so the new 80 gallon vertical is located in the back yard. The tank is tapped at the top with 3/4" iron pipe and a flexible section (to help reduce noise and prevent straining the pipe with vibration) that runs over to a vertical section against the wall. I put a drain valve in the bottom of the vertical section, but I almost never get more than a few drops of water out of it. The run from there to the garage wall is also 3/4" iron and sloped so any condensation will run back to the drain. In theory, the big pipe ensures that the air is moving relatively slowly, and so has more of a chance to cool down and drop it's water. Inside the garage, it runs through a regulator (usually set to 90 psi) and water/oil trap. I've gotten a few drops of oil out of the trap, but never any water. Haven't done any painting yet, but the blast cabinet seems much happier and I don't get water spitting out of the air tool exhaust.

Eventually, I plan to install automatic drain valves at both the compressor and the nearby water trap; but haven't done so yet. I also want to remote the compressor power, so it comes on with a switch in the garage. I installed a contactor in the breaker box to control the compressor, but haven't run the control line yet (so I have to walk to the back yard and flip the switch for the contactor).

 

[George_H]

I prefer copper over iron for this. No rust worries. Larger is always better, but 1/2 should be fine. Just be sure that you can get to the drain on the tank easily.

 

[Deleted member 12521]

Randall, George, thank you gentlemen. It sounds like I'm on the right track.

 

[weewillie]

Definitely fit an automatic drain on the tank. I did on mine and have never looked back, when the pressure in the tank gets to 4lbs it drains automatically

 

[TRMark]

I used a raiser to feed each air outlet. The other outlet is towards the end of the run, it feeds a hose reel and another large hose for painting and blasting this line has a water separator and a desiccant filter. The straight pipe runs a slightly down hill angle and drains at the end. I used 1/2" steel pipe. When the compressor gets hot it will put out a lot of water. I have been using a small soda blaster without any problems.

 

[DrEntropy]

The home rig here is a three generation hand-me-down, black pipe manifold joining three old steel fire extinguisher tanks together. It takes up less space than a large single tank and a petcock at the "low" side of the manifold drains it well. A dessicant filter and separator ahead of the regulator on the outlet for paint guns and blaster helps in the Florida west coast humidity. But the effort is continuous, dessicant must be dried (a large "cookie sheet" and heat lamp) regularly. After about five years the couplings need replacing as well.

In the shops I've plumbed we used schedule 40 PVC for the runs to workstations, risers as Mark's install at the various drops.

 

[PAUL161]

In the shops I've plumbed we used schedule 40 PVC for the runs to workstations, risers as Mark's install at the various drops.

Doc, How much air pressure will schedule 40 PVC take? I know I've had 130 lbs of water pressure in schedule 40. Do you know the bursting pressure? PJ

 

[TR3driver]

Most sources today say not to use PVC for air lines. Apparently it can turn brittle over time, and shatter violently. OSHA allows it only if the pipe is buried or otherwise enclosed to contain the shrapnel.
https://www.osha.gov/dts/hib/hib_data/hib19880520.html

Also, although Sch 40 can handle lots of pressure at room temperature, the rating goes down dramatically with temperature. At 140F (which isn't all that hot), the rating is only 1/5 of that at 73F.
https://www.engineeringtoolbox.com/pvc-cpvc-pipes-pressures-d_796.html
https://www.harvel.com/piping-syste...rial-pipe/schedule-40-80/temperature-derating

 

[RossL]

I used a raiser to feed each air outlet. The other outlet is towards the end of the run, it feeds a hose reel and another large hose for painting and blasting this line has a water separator and a desiccant filter. The straight pipe runs a slightly down hill angle and drains at the end. I used 1/2" steel pipe. When the compressor gets hot it will put out a lot of water. I have been using a small soda blaster without any problems.

Any reason why the vertical line runs above the horizontal line?

 

[TR3driver]

Any reason why the vertical line runs above the horizontal line?

I believe the idea is to keep any water in the horizontal line from running into the vertical line.

The problem is that, when you compress air, it can't hold as much water vapor. So what comes out of the compressor is hot, relatively moist air even if what went in was dry. Then when the air cools in the plumbing, it lets even more moisture condense out. In effect, it rains inside the pipes! Not such a problem if you're just running an impact gun, but liquid water causes problems if you are trying to paint or sand blast, etc. So the whole plumbing system should be arranged to keep water away from the work as much as possible, and provide places to periodically let it out.

 

[TRMark]

I believe the idea is to keep any water in the horizontal line from running into the vertical line.

That is correct & it works. Very little moisture comes out of the bottom of the vertical. A lot comes out of the end of the horizontal when drained.