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Compressed air distribution

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  • Compressed air distribution

    I'm going to make a distribution line for compressed air in my garage shop.

    The air pressure will be about 175psi, the longest run is about 60ft, the flow- up to about 22 CFPM.

    I want to make it out of copper pipe. The questions are:

    1. Will type M work reliably or I need to buy type L copper pipe?

    2. Will 3/4" pipe be sufficient?

    3. What drain and air valves would you recommend? I was looking into brass ball valves sold at Home Depot, but I'm not sure about their pressure rating.

    4. What would you install on the outlets: threading connector for the regular hose, some kind of quick disconnect or anything else? Let's put it this way: I have the end of 3/4 pipe and need to know what to attach/stack to it (air valve and all connectors that follow).

    5. What type of flux and solder would you recommend to make the job easier and air tightness more reliable?

    Thank you.
    WI/IL border, USA

  • #2
    When copper pipes are full of water ..there isnt any air and almost no corrosion takes place ..

    when they are full of air and condensate ..i think they will corrode ..and in 5 years times youre going to be getting holes in them.

    i wouldnt trust them with 50 psi in them never mind 175 psi.....i dont know the wall thickness in the usa ..but here its less than 1mm

    mine are thick walled steel...known as black iron, here in the uk.

    all the best.markj


    • #3
      I remember from my fluid power class that copper pipe is not recommended for either pneumatics or hydraulics and I also know there are those who will disagree. The reason I was given is the copper tends to become brittle over time.

      I'm guessing your wanting to avoid black iron due to rust issues. There is a cabinet maker in town who went with plastic tubing for his air lines and he loves it. Easy quick connect type fittings that do not leak and installs easily with just a tubing cutter for cutting to length.

      I think this is the brand he used:

      However, I do not know if the size you need to carry the SFPM is available in plastic. Nor am I familiar with the PSI ratings.

      To determine your sizing requirements I recommend getting a copy of Audel's Millwrights technical manual. It has all sorts of information.

      I would also assume the techs @ Rapid Air should be able to help with the sizing.

      As to HD valves, probably not at 175 psi.



      • #4
        Originally posted by aboard_epsilon

        when they are full of air and condensate ..i think they will corrode ..and in 5 years times youre going to be getting holes in them.

        If that were true, pennies would corrode, copper wire would corrode where it's been stripped of insulation. Also, copper pipes would corrode from the outside inward, especially cold water pipes because the condensation is greater. None of that happens as far as I have experienced. I think copper would be fine as long as it's not in a particularly acidic environment.


        Appearance is Everything...


        • #5
          Air line

          I put 3/8 id air hose around the top of my shop, its 30 x 30 ft.. The compressor is in one corner. I ran a line from the compressor to a brass tee and branched off with hose barbs and hose clamps. Cut the line and put a tee everywhere I wanted a hose to hang down. Put a quick connect on the end of each hose hanging down to each machine and workbench. All quick connects are the same kind. I've had this system in place for 10 years now, it's working great. Got all the brass fittings,hose clamps and hose at HF for cheap. I have added a couple of lines over the years, it took a few minutes to cut the line, insert a tee with hose barbs, hang a hose and go. I'm running a 5HP 80 gallon compressor at 150 PSI. It does everything I need.
          Kansas City area


          • #6
            This might be helpful:


            • #7
              Thats not much air line to run, use the biggest pipe you can, it works like a tank by holding volume. I would go with black iron pipe, its easy to add on a new leg or drop. it wont go bad in 5 years or maybe 20 so the rusting out problem is unfounded unless you plumb it all wrong so it traps water. If you run a CNC then you should have an air dryer anyway.

              Im not saying dont go copper , its nice but the cost benefit would be almost nothing. never us CPVC or PVC, one small fire in the shop and the whole works will be saggy plastic and every inch of it will be trash.


              • #8
                My goodness! 22cfpm @ 175psi !!!!
                What are you going to use for a compressor? Some type of scroll or screw compressor?

                Here's a link from TP Tools website that may be of interest:

                They don't reccommend copper, but black pipe.
                JHC Dayton, OH


                • #9
                  Originally posted by Jim Caudill
                  My goodness! 22cfpm @ 175psi !!!!
                  What are you going to use for a compressor? Some type of scroll or screw compressor?

                  Here's a link from TP Tools website that may be of interest:

                  They don't reccommend copper, but black pipe.
                  Agree ..If you have 20 CNC machines you would have an air dryer anyway. at that point you may as well spend $10,000 on a real air dryer anyway. so black iron pipe works just fine.


                  • #10
                    I installed 3/4" copper pipe about 8 years ago in my home shop and haven't found any problems. I used mid-grade (L) copper and a silver bearing solder. This is fed by a 5hp 175 psi Quincy compressor. However, I run the lines at 120 psi, not 175. Unless you actually need the higher pressure at some point of delivery, I can't see any advantage in the extra pressure.

                    In addition, about 100' of pipe snake back and forth on one basement wall (behind cabinets) to provide extra cooling, with a drain at the bottom. This certainly wouldn't be necessary or advisable if you decide to add a chiller instead.

                    First, corrosion isn't a problem. Short of stainless steel, you won't do better than copper.

                    Second, the 3/4" copper pipe has more than adequate pressure rating. Heat and standard 50-50 lead solder joints would be the weak link.

                    Third, concerns had been suggested about vibration affecting solder joints. A large ID bit of flexible tubing connects my compressor. I haven't had a joint fail anywhere in the system -- and it probably includes 200' of pipe and scores of soldered connections.

                    You're trying to run a bit more CFM. 3/4" should still be adequate, especially for reasonable length runs. Your valves and quick disconnects will be the gating factor. If you think you might need more air in the future, 1" type K (heavy) copper would provide some headroom -- but at that point the cost factor might suggest black pipe.

                    I put about a dozen quick disconnect air outlets around the shop, garage, and deck; and about four drains with ball valves at the low points. One nice thing about copper is that the stubs sticking outside won't rust.

                    The quick disconnects were high quality units and directly piped in. There's a very slight leakage at some of these or perhaps the compressor valves; not audible but enough to drain the compressor tank in about one day+ with the motor off. In retrospect, I still probably would not place a ball valve in front of each coupler, though many might recommend this. You surely do, however, want high flow and high quality couplers.

                    All in all, I can't imagine anything much better than copper for a low flow (under 25 cfm) system. At higher flows, the cost of larger pipe probably becomes prohibitive.
                    Last edited by PeteM; 08-02-2010, 06:57 PM.


                    • #11
                      Id recommend the standard cheap 1/4" NPT couplers for your air hoses.. try and get the type that stay snaped back once released (So you can insert hoses one handed.. kinda), And you'll want a 1/2" coupleing somewhere for any heavy use applications..
                      Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.


                      • #12
                        Heat isn't an issue for soft solder joints if they're coming from the tank and not the compressor outlet. If you use silver-braze, etc, you will use enough heat during joining to anneal the copper at the joint, reducing the rated pressure by 40% or more. Of course you're starting with a pretty high rating anyway for type L and even after annealing it should handle 175psi.

                        If you already have the copper, I'd certainly use it although 1/2" would be plenty big enough for the system you describe. I LIKE copper air lines and I use Watts brand ball valves for the shutoffs and drains. They're fine at 175psi too.
                        Last edited by chipmaker4130; 08-02-2010, 06:26 PM.
                        Southwest Utah


                        • #13
                          Copper pennies and stripped wire do corrode in a damp environment like a air line.

                          Do you have anything that actually runs at 175? If not turn it down to 100-120. You will save energy by not pumping that high. The higher pressure you pump to the more energy you waste getting it there. And your compressor will last longer.


                          • #14
                            I am in the dry cleaning business and have had a system in place with black pipe for 19 years and zero problems, at least from the black pipe. My suggestion is to run extra T's with a plug wherever you think you may need a tap in the future. I built a new plant 2 1/2 years ago and ran it all in ridgid copper. Looks fantastic but not as easy to expand.


                            • #15
                              Type M copper pipe is prohibited by code for use with compressed gases in nearly all jurisdictions. Use it and invalidate your insurance as well as violate code.
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