PVC and Compressed air

Discussion in 'Plumbing Forum, Professional & DIY Advice, Tips & ' started by rockycmt, Oct 21, 2008.

  1. Redwood

    Redwood Master Plumber

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    http://www.osha.gov/dts/hib/hib_data/hib19880520.html

    http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=INTERPRETATIONS&p_id=20202

    And you my friend are the recipient of todays award!

    [​IMG]

    It always amazes me that someone when presented with overwhelming evidence that the position they have taken is wrong, and the opinion is shared by many others will continue to argue their point...

    There must be a word for that...
    Last edited: Oct 22, 2008
  2. hj

    hj Moderator & Master Plumber Staff Member

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    Pvc

    You are quoting a rating for PVC when it was new. As it ages it becomes brittle, and will rupture at a much lower pressure. Few compressed air systems work at more than 125 psi, but there have been countless failures of PVC air systems, ALL using schedule 40 or 80 pipe, occassionally with fatal results. But I guess what we should have done is say, "DON"T DO IT!" and then let you do whatever you want to. I guess saving a couple of dollars in material costs is MUCH more important than having a safe installation.
    Last edited: Oct 23, 2008
  3. Southern Man

    Southern Man DIY Hillbilly

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  4. Southern Man

    Southern Man DIY Hillbilly

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    Location:
    North Carolina
    PVC gets brittle how, exactly? Sunlight, right? There's not much of that on the ceiling of my garage. Maybe you should check where the failures have occurred. My guess probably during testing, and a pipe was nicked or weakened by the guy installing it.
  5. Furd

    Furd Engineer

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    Location:
    Wet side of Washington State
    I had a PVC compressed air distribution system in my garage workshop some 35 years ago. I never had any problems with it but that doesn't mean it was safe. One thing that I did was to have a flexible hose between the compressor storage tank and the fixed piping to eliminate vibration and stress on the PVC. Very early on in the use of PVC piping it was discovered that repeated vibration OR stress induced by forcing PVC piping into alignment was a major cause of early failure.

    When I learned that Washington state (through the bureau of Labor and Industries) had prohibited PVC in compressed air systems I discontinued using the PVC air line in my shop.

    In my NOT so humble opinion, given the results of years of testing and the high failure rate of PVC piping in compressed air systems, only a fool would use PVC for compressed air.

    There is another possible factor in the high failure rate of PVC compressed air piping and that is that all oil-lubricated compressors have a certain percentage of the lubrication oil carry over to the air. There is no doubt whatsoever that petroleum products are detrimental to PVC. Just one more reason not to use PVC for compressed air systems.


    I'm quite sure there are hundreds of home shops that have PVC piping in compressed air distribution systems and they have had no failures. I personally know of someone that installed a PVC distribution system and even after I told him of the Washington state prohibition he dismissed the danger just as Southern Man is doing. Just because some people are lucky is no reason to tempt fate.
    Last edited: Oct 23, 2008
  6. Gary Swart

    Gary Swart In the Trades

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    I liken this discussion to what many woodworker make when rationalizing the non use of blade guards and splitters on their table saws, or some drivers make about seat belts. They feel since they have not used a blade guard in (fill in the years) they some how are immune to the danger, or they have been driving for 50 years and never have need a seat belt. You can make all the BS excuses you want, PVC is not a safe material for compressed air and it's stupid not to buckle up. Southern Man, you can use all the PVC you want in your shop for compressed air, but please do not advise others to do so.
  7. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    The system isn't used very often and when it is charged, is connected via a rubber hose and quick connects. The oiler is located on the end near my bench so doesn't contaminate the system that can be used to inflate tires. Comparing it to driving without a seat belt or cutting wood without a guard, or owning a live lion is rather silly but if it make you feel good I'm happy for you.
  8. hj

    hj Moderator & Master Plumber Staff Member

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    Osha

    Just because OSHA rules do not apply to homeowners, does not make it safe to disregard their advice. Your best source is to call your state's industrial safety division and ask them if there have been any incidents in your area of bursting PVC air lines, because obviously you are not going to believe us. I hope you do not do your own plumbing systems, because few people with your "I can do what I want to", attitude install them correctly.
    Last edited: Oct 23, 2008
  9. Furd

    Furd Engineer

    Messages:
    446
    Location:
    Wet side of Washington State
    Southern Man, you claim to be a civil engineer. Would you not adhere to ASTM specifications for reinforcing steel in a bridge you designed?

    Would you ignore the specifications for a steel I-beam used to support some structural part of a building that was being remodeled to open up a room? How about if the building was a residence that had lally columns in the basement holding up the main floor and the architect had a structural engineer calculate a specific steel to spread the load to the outside walls. Would you just substitute a steel stud because steel is steel?

    How about a gas grill connected to a natural gas line? Would you use a piece of air hose that had a 200 psi maximum use pressure with a 800 psi burst pressure? Would you justify that usage by saying that the natural gas is less than 1/2 psi pressure? Would you use a piece of garden hose to connect a furnace to the gas line using the same justification?

    Admit it, you don't give a damn about specifications when the specifications might somehow inconvenience you. I's glad you live on the other side of the country from me and I will never have to subject myself to ANYTHING you might have had a part in engineering. In short, you are a disgrace to all engineers.
  10. Steve_P

    Steve_P New Member

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    41
    Location:
    East TN
    the pressure rating of PVC and the resulting factor of safety is meaningless. The fact is that PVC is NOT intended for compressed air use and the makers state that. I'm sure there are miles of PVC being used in compressed air systems in people's garages, but it's still not a smart thing to do. Catastrophic failure will not be friendly to anyone around. The only time I would ever consider using PVC for compressed air is if it was buried underground- where failure couldn't cause personal injury.
  11. Southern Man

    Southern Man DIY Hillbilly

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    Actually, your analogies are all invalid. There are plenty of old structures that don't meet current specifications and are performing fine. In fact, many current standards are designed using these as an empirical basis. As one who claims to have experience, I'm surprised that you don't know that. ;)
  12. Redwood

    Redwood Master Plumber

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    Can you say, "I've adopted an indefensible position?"
  13. Southern Man

    Southern Man DIY Hillbilly

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    530
    Location:
    North Carolina
    Sure you can. You can also say something derogatory about corn mash. :D
  14. Redwood

    Redwood Master Plumber

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    No need...
    Your doing great on your own...
    Keep talking....:D
  15. Southern Man

    Southern Man DIY Hillbilly

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    Location:
    North Carolina
    Gotta love the guys who "know the code" but don't have a clue about the engineering principles behind them. In their minds they are never wrong. ;)
  16. Redwood

    Redwood Master Plumber

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    Location:
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    Like the fact that air compressors have a tendency to have a small amount of oil from the compressor in the air and many of these oils have proven to adversely effect PVC.

    The only compressors that would not have this oil in the air would be a much higher quality than what you have in your garage...

    It's great that you know more than the engineers at Charlotte pipe but I'll stick with their advice...

    Here's your shovel keep digging!

    [​IMG]
  17. Bill Arden

    Bill Arden Computer Programmer

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    584
    Location:
    MN, USA
    I'm not going to touch the whole PVC debate since I will admit that I don't know enough to say if PVC will degrade...

    Personally, I would not trust all those glued PVC joints not to have small air leaks.
    And then there is whats called "the creep rate" of most glues.

    However as I said before there are other plastics that are approved for air lines and, as I understand it, the original poster just wanted a cheaper solution than copper or steel.

    So back to the original question.
    1. Yes it is possible to use a plastic pipe, but you have to use the right type.
  18. hj

    hj Moderator & Master Plumber Staff Member

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    Location:
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    air

    The original poster wanted to use PVC because he already had it, not because he wanted any other type of plastic. We gave him the recommended answer. What he or anyone else does with it is beyond our control.
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