compressor air lines

Discussion in 'Remodel Forum & Blog' started by Master Brian, Oct 5, 2009.

  1. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    I am wanting to setup outlets for my compressor, so that I can plug my air tools in without having to run long hose everywhere.

    Most of this will take place inside of my 1-1/2 car garage, but I am toying with the idea of also running a line into my house and into the mechanical room in the basement.

    I should note the garage is not attached, it sits about 10' off the house, but I have an area I can easily bury the line and bring it into the house.

    What have others found that works well? I was thinking of using PVC, someone mentioned the grey plastic pipe, but a google search just brought up to use black metal pipe. Here is a link to that site.

    When I had my drive re-poured last year, I ran metal pipe under ground and terminated it in my garage and at the edge of a box-out crawl space. I did that so that if I ever wanted gas to heat my garage, the line would already be there. I suppose I could use that and then when I get done remodeling or if I ever wanted gas in the gargage, I could switch it's use back over.

    Thoughts???
  2. Gary Swart

    Gary Swart In the Trades

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    7,298
    Location:
    Yakima WA
    Absolutely do not use any kind of PVC for compressed air. PVC becomes brittle overtime and is prone to burst under air pressure. I know it is tempting because it is easy to assemble and cheap to buy, but you are tempting fate if you use it. Without getting into the professional air lines that are excellent but very expensive, there are two acceptable media that you can use. Black iron and copper. My personal choice is copper because it does not rust and is much easier to install. Copper assembles like PVC except joints are soldered rather than being solvent welded. Black iron will rust and while probably not rust to the point of leaking air for many years, it will produce some rust inside that could contaminate tools, especially paint guns.
  3. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    It's amazing how much water can accumulate in the bottom of an air compressor after running on a hot humid day. Stay away from steel or iron. Even with a dryer, you'll be constantly allowing some moisture into the line, and rust is inevitable. And, as noted, using PVC is tempting fate...the shards can kill.
  4. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    Well, PVC is definately out for me.

    I actually was also wondering about pex as well. It's very strong, wouldn't be many joints along a long run, and it's flexible, which equals easy to run. Though I've thought about it, I am 99% sure I wouldn't use it.

    The link I attached above, suggests staying away from copper because the joints can come loose. I question that, as it's used for water and I'm fairly certain my water pressure is around 90psi in my house. Of course my compressor goes to about 120psi and I plan on a 2stage once I get my garage setup.

    I would think the black pipe would rust as well, but in my area they use it for gas and it seems to hold up, here is what they say....

    Use Black Iron Pipe only. We do not recommend galvanized metal pipe, as galvanization can come off the inside of the pipe, clogging
    separators and regulators. Do not use plastic pipe, as plastic will not help cool the air; and glued joints often separate. Avoid copper
    tubing, as it is easily damaged; and soldered joints can come loose under pressure (Safety Hazard). Use 1/2" pipe for up to 75 feet of
    horizontal runs of pipe from your compressor. Use 3/4" pipe for horizontal runs of over 75 feet.


    So, at this point, I guess I am leaning towards copper or black pipe, unless someone else has a good suggestion. Hmmm.....
  5. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    Unless I had a separate industrial dryer before it entered the black pipe, I'd use copper. Your other option is either DOT air line or high pressure hose, but I think I'd just use copper.
    Last edited: Oct 5, 2009
  6. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,298
    Location:
    Yakima WA
    My copper air lines have been holding strong for several years. I question that pressure will cause the joints to fail. I you have 90 psi in your home, that's way too high. 60 to 65 psi is plenty. Higher and you risk rupturing hoses to the washer and toilets, that much pressure is also hard on faucets and valves. You should seriously consider a pressure regulator valve and a thermal expansion tank so the pressure can be lowered. FWIW, I run 50 psi and feel that that is plenty of pressure.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,802
    Location:
    New England
    Pex might work. The pressure it can handle depends on the temperature. You'd have to read the individual specs for the type you are interested in. Because it is flexible, starting and stopping air flow could cause it to whip around, which could wear a hole in things. Could do that with copper as well, so proper clamping and routing is critical.
  8. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,298
    Location:
    Yakima WA
    My compressor is connected to the copper line with a high pressure hose to absorb vibration and movement of the compressor.
  9. dgold

    dgold Product R&D for a powertool manufacturer

    Messages:
    82
    Location:
    Carlsbad, CA
    I've seen PVC used many times. I'm not endorsing it by any stretch, just that I've seen it used successfully in industrial applications. At cool temperatures and in smaller diameters, it has a fairly high burst strength. While I have no data to back this up, I would think PEX would fail safer than PVC since it's a less brittle material - would be interesting to test it. Personally, I'd use 1/2" copper.

    One of the big downsides to plastic vs metal (other than a potential safety issue) and why I personally wouldn't use plastic, is that it's a much better insulator than metal. Metal, being much cooler than the heated compressed air will encourage condensation along it's interior and if routed properly can help ensure extremely dry air at the outlet. Dry air is typically wanted - especially if you intend to use any kind of spray equipment. If using air tools, dry air is still wanted, but a lubricator may be added after the regulator.

    When plumbing for air, keep in mind where that water will go. If you have a giant "U" or trap in the ground, which it sounds like you may, eventually water it will build up in this trap until you eventually have accumulated a giant slug of water. If this slug of water is then driven through an air tool with a vane motor, it will undoubtedly destroy the tool. Somehow, you need to cool the air below it's dew point before sending into your underground plumbing. Don't let anyone tell you that a non-desiccant moisture filter will pull the moisture out of the air. They don't dry (dehumidify) the air, they only remove liquid water.
    Last edited: Oct 8, 2009
  10. Gary Swart

    Gary Swart In the Trades

    Messages:
    7,298
    Location:
    Yakima WA
    I have to question that you have seen PVC used for compressed air in industrial applications. OSHA would put an immediate stop to it. As far as it being used by many individuals, I know that is true, but just because many do it hardly makes it safe. If you want to take the chance, that's your business, but don't try to justify an unsafe practice just because it's cheap and easy.:mad:
  11. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    I like and have used black iron pipe. Copper would be good too.
  12. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,245
    Location:
    Cave Creek, Arizona
    air

    Copper tubing will withstand any safe air pressure in your system, "Coming apart" is not a danger with copper, it would just cause a loss of pressure. Catastrophic, spontaneous, pipe failure and the shrapnel it causes is the danger with plastic pipes.
  13. Cass

    Cass Plumber

    Messages:
    5,980
    Location:
    Ohio
    I can't wait till the first guy comes along and wants to use PEX for compressed air...
  14. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas

    I have questioned whether it would be ok or not. It would seem a quick, inexpensive and easy to run option for a home setup.

    With that said, I have read that plastics create too much water buildup that can't be removed via water seperators, so it is not an option I am willing to try.

    Although it is relatively more expensive than the copper, especially since I have lots of copper sitting unused in my house after switching to mostly Pex water lines, I think I will go the Black Pipe Option. I think I found an easy to run underground spot to come into my house via the garage and it will not contain any vertical runs except for possibly one section inside the house, which I can place a valve to purge the line of any pooled water on occaision.

    Thanks for the feedback and for helping me decide what option to go with.

    I did speak with my neighbor, who is also interested in running a line inside his garage and I think he's going to go PVC. Needless to say, I am a bit concerned now about helping him with any jobs in the vicinity of the air line.... Maybe I'll offer him my copper!!
  15. Lakee911

    Lakee911 I&C Engineer (mostly WWTP)

    Messages:
    1,328
    Location:
    Columbus, OH
    How do you figure? I would think it would be the opposite since plastic is a better insultor...no?
  16. Master Brian

    Master Brian DIY Senior Member

    Messages:
    368
    Location:
    Kansas
    I would have thought the same exact thing, but here is what I read...

    "By using metal piping of proper size, not only does the piping serve as an 'air reservoir', it also enables the moisture-laden air to cool so that the water separators can do their job." .... "Moisture condenses in the cold metal pipe and can be easily removed by the water separators." ..... "Do not use plastic pipe, as plastic will not help cool the air...."

    Basically, they are saying the plastic pipe doesn't condense and it stays more "air borne" so it isn't easily separtated, whereas in the metal pipe, I guess it condenses, thefore it can be separated.

    I thought it was very interesting. Again, I would have thought the same....
  17. iminaquagmire

    iminaquagmire DIY Senior Member

    Messages:
    207
    ON our SCBA fill stations, all the tubing is plastic. That's 6000 psi. Granted we have separate dryers and filters though. Plastics are an option, you just have to use the right ones. I'd still use copper simply because its easily available and easy to work with. Your only tools are a torch, a cutter, and something to clean the joints with.
  18. hj

    hj Moderator & Master Plumber Staff Member

    Messages:
    26,245
    Location:
    Cave Creek, Arizona
    air

    What kind of plastic is rated for 6,000 psi? It would have to be the o.d. size of 2" pipe with a hole the i.d. size of a 3/4" one down the middle. At least PEX would split, not shatter.
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