My next project

noworriesJanuary 13, 2005

Now that I've finally about finished the electrical rough-in in my shop, I'm ready to tackle the shop's first metalworking project - plumbing the air lines. I'd appreciate any observations about what you like and wish for in an air system, and suggestions on my plan below.

I plan to run 3/4" Type-L copper trunk line from my compressor, an 80 gallon Bel-Air model 218V two stage, about 30 linear feet to the water separator, then from there along the center of the trusses the length of the building. I'll then run 1/2" branches to outlets. The air chucks will be located as follows: one in center of ceiling for a retractable reel, one between the garage doors for air to the outside, and then at various locations above bench height. The lines will ultimately be behind drywall and each chuck will have a ball valve shutoff and a drain valve, as will the outlet from the compressor. I'm a little concerned about the length each assembly will protrude from the wall with both a shutoff and drain along with the air chuck. I will attempt to maintain 1/4" per foot fall in the horizontal lines.

I expect to use a sandblast cabinet and sanders, along with various air wrenches, etc. for automotive projects and whatever else comes along. I may shoot some primer, but don't anticipate doing any finish painting.

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I was doing a search for a friend who was planning to pipe his shop for air using PVC. The reason for the search was to find comments about the safety of using PVC which I already knew was a NO-NO, and I just wanted to back up my comments as best I could. Anyway, the information I found was on the Tool Shed forum, and you may want to check out that posting for information that might give you some helpful tips.


Here is a link that might be useful: Air hose reel/Tool Shed forum

    Bookmark   January 13, 2005 at 8:33PM
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I read about a nifty and low cost water separator. Run a large( 1.25 or 1.5") copper pipe from compressor to ceiling. Tee in your incoming air at the bottom with a drain valve on the bottom of the tee. The writer of the article said it makes a very good separator due to the large diameter and the copper condenses the moisture inside it.
Mike A

    Bookmark   January 13, 2005 at 10:20PM
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The 1 1/2" separator sounds like a good idea, I would put it before the manufactured filter/separator. The store bought ones can fill up quick and be a pain to drain.

The 3/4 trunk line is over kill unless you plan on using many tools at once (10 or more).

I think all the ball valves are an over kill as well. If you need to change a quick connect you can very simpily walk over to the compressor and turn off the whole system. This should be a stop and bleed valve. It will bleed everything down stream of the valve.

Take the money you save from these two items and spend it on more pipe and tees.
If I was comming across the ceiling over my bench then down the wall I would put a tee in on the horizontal run before I turned down the wall then a tee above the bench and then under the bench just below the working surface but at the front of the bench. Half way down my shop where a car might sit I would put in a quick connect up high on the wall then another one low on the wall. On the high ones I would put a 3/8" valve and a small coiled air hose. I have seen a large coiled air hose mounted on a tight wire which runs the length of the shop also. Put a drip leg at the end of each run. (don't forget to emty them now and then)

I'm a plumber/steamfitter and have installed quite a few of air systems at work and for friends. At work we use sch 40 black iron pipe but at home I use copper.

just my two cents!!!

    Bookmark   January 14, 2005 at 10:26AM
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Thanks guys: Based on this informarion and talking with the people at the "Air Tool Store" I'll nix the idea of valves and drains at each outlet. I like the idea of the larger manifold off the tank. That will reduce the air velocity although the pipe surface area increases substantially less than pipe area as you increase pipe size. You'd be better off running multiple lines in parallel for heat rejection. Anyway, the main line does go vertically from the tank to the ceiling then over and down to the water separator,then back up to the ceiling for the trunk run down the building backbone.

An additional point the sales guy made was to take the air vertically out of the trunk line then over and down to each branch run. This keeps any water in the trunk from readily running into the branches. He too said not to use PVC. Metal is a much better heat conductor, and he said that air will extract oils out of that plastic pipe. I'm not sure I concur with the last point, but the former is good advice. I'm also not sure I want 80 gallons of 175 PSI air in PVC.

Roscoe: I can't seem to follow you about the bench routing. Are you suggesting an outlet in the ceiling at say 24" off the wall with a coiled hose hanging down? Also, are you suggesting running the line out from the wall just under the bench to its front? If I read you right, these each seem like good ideas rather than just placing outlets in the wall above the bench itself. I don't get the part about the "tight wire running the length of the shop."

This will be fun. The guys at the plumbing supply said I had enough pipe and fittings to plumb a house.

One more thing. Does copper pipe need to be secured in the wall at intervals, or just attached to blocking at the bottom of the run in the wall? Its probably seven feet from the top plate to the bottom elbow.

    Bookmark   January 14, 2005 at 2:22PM
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I would not put a coil above the bench but in other spots it might be handy. At one side or maybe two sides of the bench I like to run a outlet right at the front corner of the bench. Grade the horzontal runs and tee off the verticals with a drip leg below. This drip can have a simple plug in it. When you want to blow the moisture out of the system you turn off the stop and bleed, pull out the plugs, then ease on the air again. This moisture may have rust in it, so you might want to hose it into a jug.
The tight wire is a cable that runs the length of your shop and is tightened by a turnbuckle. You put an out let at one end and hook in an end of a coiled hose. The cable runs through the middle of the coil. The female end of the coil can run freely down the cable. At this point you still need about 10' of stright hose to go off the end of the coil. The coil will not uncoil or recoil, just run up and down the cable. This can eliminate alot of pipe sometimes.
If you can take the branches off the top (45degrees is good ) then all the better.

The compressor will produce two things air and heat. The heat will disipate throughout the system. I dought that you will use enough air that you will have a heat problem.

Make sure you secure the ends of the piping well (they may get pulled on) the rest of the system secure as normal.

Good luck

    Bookmark   January 14, 2005 at 10:30PM
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We had a moisture problem at work (in Arizona!!). To eliminate the problem, we pitched the line downwards towards the far wall on our horizontal runs. We also oriented each tap tee up, than 90'd over and 90'd down. The end run 90'd down and had a water drain below the quick connect.

    Bookmark   January 15, 2005 at 1:49AM
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My shop compressed air is plumbed with galvanized steel piping. It's been in use for about 40 years, with no sign of corrosion. And little moisture in the lines.

When you consider that the pressure storage tanks are plain steel, I'm not sure there is much need for concern about internal pipe corrosion.

I also would never use PVC for compressed air. It gets brittle when cold, and compressed air gets very cold when it goes from high pressure to low pressure.

    Bookmark   January 15, 2005 at 11:34PM
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Our compressor in the fire hall is plumbed with a filter and water separator just beyond the outlet of the tank and before the lines go out to the main air runs. Most all moisture remains in the tank until it is drained off manually. Very little moisture gets to the filter. For what may remain after these trap points, I don't think wouuld require any additional trapping at the outlets since none of the air is used for critical uses such as painting. If moisture was a concern for painting, a trap right at the spray gun would likely be the best choice.

Also, here is a link to PVC use with compressed air and some reports of failures.


Here is a link that might be useful: OSHA report on PVC pipe used for comp. qir

    Bookmark   January 16, 2005 at 11:04AM
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May I suggest a ball valve shutoff with bleed down on the quick connect side for each run should you ever have a failure and need to change redo etc. Also a six to ten inch drop at each outlet and a drain valve at the bottom below the fitting will halp keep lines clear and free of moisture, as well where your compressor feeds the main line a flexible line ie.large diameter air line and quick connects will help isolate your compressor vibration from ridged lines. Poly air line tubing is flexible and easy to route I also placed my quick connects just below the bench top so as not to have the flex lines laying on top of where I need to work. Just me 2cents worth/


    Bookmark   January 17, 2005 at 9:14AM
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