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Air line

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  • Air line

    We need to run an air line underground about 25 feet, from a centrally located compressor. One line goes into the building right away, the other has to go underground across the yard into another building. We want to put the compressor outside against the wall of the first building, and we'll be making some kind of outdoor housing for it, to control noise and to keep it cleaner. I'm thinking of using copper line and direct burying it. Before I do anything, I would like to hear the correct way to achieve this.
    One problem I can forsee is that the line would be lower than the building it's entering, so water removal could be a problem. If I make a drain at the low spot, that would have to be outside, and I would have to build a pit where the valve could be. That pit will fill up with water from rain, etc. The water table is very high at this place. As far as the land goes, there will never be any vehicle larger than a lawnmower that would cross where the line has to go. I'm wondering here about how deep we should bury it. Below frost of course, but here that's about 6 inches, possibly excepting an unusually cold spell. We were thinking about 1 foot.
    Another question is safety- will it be ok to situate the compressor/tank against a wall of the main dwelling? Should there be any kind of barrier between the house and tank?
    Wiring it is no problem, and I think we might put a light within the enclosure we build, partly for visibility, and partly to keep some small heat there for rust control.
    Last question (for now) is should we raise it above ground and by how far? It will be in a dry spot under a deck already, so maybe just a concrete pad is what I'm thinking. It's an upright tank with compressor on top, and we are using it at about 120 psi. The extended line is for a lacquer spray gun and a drilling machine, which doesn't take much air. Only one of these can be in use at any one time. The short line into the house (shop) will be powering a pin gun and a staple gun, no other air tools, except a nozzle to blow dust around with.
    What do you guys think of all this?
    I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-

  • #2
    I never let my compressor get too cold, that can cause all sorts of problems beside condensation in the tank. Direct bury of copper is a major no no. Way too much shrinking and expanding for the joints, plus copper will corrode rapidly in the ground. Have you thought of putting 4 inch PVC in the ground, just use normal air hose through the PVC and leave yourself some room for running future wiring? Remember to put a couple of draw strings through the pipe while you are putting this together.

    If you live in an area that has below Zero Celsius weather, I would go 18 inches deep or deeper. You can rent a trencher to do this type of work, it is a lot easier than a shovel.



    • #3
      I'll be doing the same at work next summer since we are build a steel out building to house our machine shop. We have a large rotary screw and want to use it's air for the new shop. I contacted a plumber friend about this and his recommendation was 3/4" copper HVAC line which is flexible and come it a coil. As far as drainage I won't have to worry since the compressor has a chiller/evaporator, water separator and oil separator in addition to a large tank mounted below the compressor. In your case I would run the line downhill to either building and have an inside drain setup.

      Edit: I forgot to mention that I was running the air, data, phone and intercom lines thru an underground PVC electical conduit like stated above. This means corrosion won't be an issue in my case.

      -Christian D. Sokolowski

      [This message has been edited by rsr911 (edited 12-16-2004).]


      • #4

        As that I am Columbus, and have been in the Akron area many times. I know what your weather and ground is like.

        You want to think of this like a water pipe between buildings and put it real deep. Plus have some way to keep you PVC from collecting water, which may cause corrosion. I would take 5 pounds of ductseal and make a temporay cap on the up side of the pipe and use compressed air to blow everything out of the pipe.

        Also remember that open pipes can become of little critters. So some wire mesh on each end may solve that situation.

        My experience is from supervising boring teams that went under roads and small buildings. Sometimes I would come back a year later and find that we had tenants.



        • #5
          Thanks Jerry.

          I was hoping to glue it together with PVC cement. I had alsp planned on bringing each end into a large electrical enclosure from which I could branch out the various communictions lines, I figured I run the air straight up thru the top of the box and attach fittings as necessary. Now I'm just trying to figure out if I can run the 3-phase in a trench and if so can it be the same trench. We plan to bury this at least 36" deep so there are no issues in the future. The power lines will have a disconnect at each end for safety reasons.

          Anyway back to the original question, I've used hard copper all over my shop with a 150' 1.5" trunk line down the middle, every joint is a T with a 3/4" valve soldered in line and the unused ones capped. The copper works great and is easy to work with. I figure if the flexible HVAC copper can be soldered to regular joints it's got to be the easiet way.

          -Christian D. Sokolowski


          • #6
            I think I'd use flexible reinforced plastic tubing for the air line, or just a regular flexible air hose. I'd run it inside some plastic electrical conduit, both for protection and to make it easy to replace, if and when. If you need wiring, you could run the wires in the conduit, too.

            Depending on the kind of soil you have, I'm afraid copper might corrode over time.

            [This message has been edited by SGW (edited 12-17-2004).]
            Try to make a living, not a killing. -- Utah Phillips
            Don't believe everything you know. -- Bumper sticker
            Everybody is ignorant, only on different subjects. -- Will Rogers
            There are lots of people who mistake their imagination for their memory. - Josh Billings
            Law of Logical Argument - Anything is possible if you don't know what you are talking about.
            Don't own anything you have to feed or paint. - Hood River Blackie


            • #7
              Thanks for the responses. I don't know why, but I never thought of running air line in a pvc pipe, that's probably the best way to do it. It makes sense as well to run some other wiring, even though the outbuilding is wired for power. We could certainly use an intercom and a link to the house's doorbell.
              My reasoning for using copper came because my water feed from the street is direct buried copper, and I haven't had any problem with it corroding. Maybe that's just because there's little alkali or other such component in the ground around here. I like the pvc idea better, anyway. I will avoid the use of right-angle junctions, and instead use curved sections of pvc to make the horizontal to vertical transitions at each end of the pvc tube. This will make it way easier to feed lines through it, and to clean it out should that become an issue.
              Something else I might mention for anyone running wires, etc, inside another pipe. Baby powder makes it way easier to feed the lines through. Vacuum one end of the pipe while dusting the powder into the other end. When the vacuum cleaner starts smelling like roses, the powder has made it along the length of the pipe. Don't vacuum it all out.

              [This message has been edited by darryl (edited 12-17-2004).]
              I seldom do anything within the scope of logical reason and calculated cost/benefit, etc- I'm following my passion-


              • #8
                I used to use Ivory Liquid for my snake snot, the baby powder probably works well. To bring the ivory liquid bad to life, just a little water in the conduit and will come back.

                Copper pipe used for direct bury water lines is different that most house hold pumping, but I can remember why.



                • #9
                  Around 30 years ago I bought some nylon air brake line when the Reo factory went out of business in Lansing, and I laid it 1'deep, from the garage to the small shop 50' away still there still working


                  • #10
                    <font face="Verdana, Arial" size="2">Originally posted by jfsmith:

                    Copper pipe used for direct bury water lines is different that most house hold pumping, but I can remember why.
                    In the UK copper pipe for water service pipes came in 60ft coils and was in a soft state.It was to be laid in a trench at least 2ft 6ins deep against frost.It is meant to wave from side to side in the trench to allow for any ground settlement pulling it staight.

                    Jointing was by a soldered capillary fitting or a manipulated compression fitting. I.E. the tube was swaged to prevent pulling out of the coupling.

                    Copper pipe for internal use in 20ft(6m) lengths is in a half hard state.



                    • #11
                      There is nothing wrong with copper or Pex,just don't use pvc for airlines,it sucks.

                      I used plain vanilla black iron or galavanized pipe.No need to thread anything yourself,if you need a 90* bend then do just that ,bend it,you get better flow that way anyhow.Both come in standard 10 and 21' sections with threads on each end.
                      I just need one more tool,just one!


                      • #12
                        I don't buy into that burying copper in the ground is a NO! NO!

                        Copper for direct burial has been used for years, if not decades. Is common practice for the propane dealers to run copper tubing from the tanks to the houses or out buildings.

                        You will find one inch copper tubing used for water line from well to the house all over this country.


                        • #13
                          First, I would watch out for HVAC copper tube, it has very thin wall thickness compared to rigid copper, or normal copper tube in coils.
                          To solve the condensation problem in the line, there are several solutions:
                          1. The first is to install a "dust leg" at the end of the line (like you see in gas lines).This would be a 4 or six inch pipe downward and at it's bottom, tap off with a small 3/16 or 1/4" copper line that comes back up along side the main line, and is used to blow off the water.
                          2. when you come up put a Tee in and feed your appliences with the side leg. take the vertical leg and put a full size ball valve on it , then you can "Blow" the whole line using the ball valve..just remember to do that, you need lots of volumn, and any elbows will slow the air down. we took the discharge and ran it right through the roof, buit you can do other stuff.

                          Last ..the compressor /building
                          Do not let the compressor or pad touch the building if reduce noise.
                          Next, the line going down to the ground from the compressor should be a Stainless Steel flexible hose, with a loop or zig/zag in it so the ground can heave or pad move without stress on any component. These are availble and used in many commercial units.
                          last,put a 25 watt heater on the CRANKCASE of the compressor for winter operation. do this for two reasons, when it starts, the oil will flow, and most important, if not used for a while, and you have leaky rings, water will wind up in your crankcase oil because it is colder than the head at start up.


                          • #14
                            I run compressed air all over my place - it sure is handy. Just use nylon or PE tubing. You can get it up to 1/2" size when using one-touch fittings or smaller works well if you put a resevoir tank on the receiving end.