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Thread: Flushing copper piping used for compressed air?

  1. #16
    Also, from what I understand, PEX can't be installed where it's exposed to sunlight. Good thing that it has to be installed inside of a wall cavity because the installation is butt ugly IMHO.

  2. #17
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    Quote Originally Posted by Steve Mathews View Post
    Also, from what I understand, PEX can't be installed where it's exposed to sunlight. Good thing that it has to be installed inside of a wall cavity because the installation is butt ugly IMHO.
    I was looking for information of PEX failure modes and didn't really find anything. I did find what you say about sunlight. Memory says PEX shouldn't be stored outside for more than 6 months before being installed.

  3. #18
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    Some years back I half choked at the cost of copper for air lines. Until I saw what 'some people' were willing to pay for some snazzy anodized aluminum tubing and fittings. Yeah, PVC is to be avoided, unless you can find the proper stuff to use. We had a 'large' (1-1/2 to 2") line vanish into dust one day. Big bang and not a piece to be found. Or so they said. Which I thought to be impossible.

    Threaded anything sucks IMO, with regard to air lines. I even used soldered ball valves in mine. Which of course made them not worth saving when I tore it out. Depends a lot on the quality of the threads. Some of the hardware store fittings are awful and shred the tape screwing them together. And I had no luck at all with pipe compound. Loctite has, or had, a hydraulic sealant that looked promising, but I was unable to find it when I looked.

    Guy I worked with a couple years back had redone all the plumbing in his house with the latest plastic tubing. And years later it failed, and of course the company that had offered it up with a lifetime warranty was bankrupted off the planet. Cost him a ton to replace it. So he was skeptical of any new-fangled stuff coming along after that. And I'm kinda leery myself.

  4. #19
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    PEX is not PVC, or that CPVC stuff that failed so dramatically in Wes's co-workers house. PEX is a cross linked polyethylene, meaning that it is a lot stronger and has a memory. PEX A is an expansion fitting system that uses a mechanical expander to stretch the pipe over the fittings. Fittings can be either copper or plastic. I generally use the plastic ones as they are much cheaper and have been proven reliable.

    When I install a PEX system in one of the houses we build, I cap it all and pressurize with as much air pressure as I can get out of a jobsite compressor. I use a manifold that has a schrader valve and a gauge so I can monitor pressure over the next few weeks or months as the rest of the house goes together. It's surprising how much temperature changes effect the pressures. It's also really obvious if a screw hits a water line or something. I've been using this system for 5 years or so, and it is by far the best there is right now.

    Yes, I'm comfortable using it for air lines in my shop. In my 9-5 I've seen many leaks and failed fittings in copper and steel pipe, exactly one in PEX A (factory blem). It's cheaper, faster, and I think it looks nice when care is given to it's layout. YMMV

  5. #20
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    Quote Originally Posted by Curt Harms View Post
    I was looking for information of PEX failure modes and didn't really find anything. I did find what you say about sunlight. Memory says PEX shouldn't be stored outside for more than 6 months before being installed.
    There will be no problems with PEX surface installed in a room with windows. There are ongoing manufacturer tests regarding UV breakdown, all plastic is susceptible to that to some extent, look at Uponor or Wirsboro websites for details. I have a stick that I've left outside in direct sun for 5 years now and it is perfect still. It's a test stick, it's beside some siding and a couple other things that I'm torture testing. The manufacturers are not wanting to repeat the CPVC fiasco, so PEX is probably the most tested plumbing product to ever hit the market.

  6. #21
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    For air lines installed indoor, why use galvanized? You can paint black pipe if concerned about ambient moisture.

  7. #22
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    Quote Originally Posted by Michael W. Clark View Post
    For air lines installed indoor, why use galvanized? You can paint black pipe if concerned about ambient moisture.
    Unless you have a real good inline dryer, the inside of the pipe would soon be a rusty mess and would tend to puke it out the other end.

  8. #23
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    Quote Originally Posted by Frank Pratt View Post
    Unless you have a real good inline dryer, the inside of the pipe would soon be a rusty mess and would tend to puke it out the other end.
    Is galvanized pipe also galvanized on inside? I thought it was just exterior?

  9. #24
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    Inside & out.

  10. #25
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    The PEX in my garage is mostly protected from sunlight but one section sees sun for about 4 to 8 hours starting in the morning. It's been in place for at least 12 years now with no issues. Moisture is probably the biggest issue. With rigid pipe you can slope it in a way to get any moisture to flow to where it can be removed from the system. With PEX there could be low spots where water will pool. If it pools deep enough a large surge in air will push it out. You can counter it, of course, with drip legs and drains along with a good dryer.

  11. #26
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    Quote Originally Posted by Frank Pratt View Post
    Inside & out.
    I have some fittings that don't appear to be, but could be they just got discolored from sitting in the store.

    I used galvanized pipe on my previous compressor setup to mount the filter/regulator.

    For my current one, I put in some copper loops to help get the moisture out by providing a little more cooling. My compressor is in the garage and gets humid in the TN summers.

    When I plumbed this system, the copper was not "that" much more than galvanized, but it sure was easier to work with for my cooling setup. Threaded piping requires a lot of unions and/or carefully planned installation sequence. Threaded fitting cost seems to add up more quickly than the copper fittings did.

  12. #27
    Quote Originally Posted by Wes Grass View Post


    Threaded anything sucks IMO, with regard to air lines. I even used soldered ball valves in mine. Which of course made them not worth saving when I tore it out. Depends a lot on the quality of the threads. Some of the hardware store fittings are awful and shred the tape screwing them together. And I had no luck at all with pipe compound. Loctite has, or had, a hydraulic sealant that looked promising, but I was unable to find it when I looked.
    An old friend of my father was an industrial plumber - think 18" + water and gas lines in steel mills in the Pittsburgh area. He also did a fair amount of black pipe air line installation and he taught me a trick to ensure air tight threaded fittings. I've been using this for years and have never had a single threaded fitting leak. There is a product you can get from large supply houses called X-pando. It's a type of hydraulic cement with additives. It comes in a can as a powder - mix a small amount to a peanut butter consistency and use it on the male threads and make the fitting. It expands to some ridiculous PSI and seals the joint almost permanently - to break apart 1/2" or 3/4" black pipe takes at least 24" wrenches. 1" takes a 36" and anything over that takes at least MAPP gas and the largest wrench you have with a long cheater bar.

    https://www.xpando.com/xpando.php

    I bought a 70 ounce can 40 years ago and still have 3/4 of it.

  13. #28
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    Quote Originally Posted by Brian Backner View Post
    An old friend of my father was an industrial plumber - think 18" + water and gas lines in steel mills in the Pittsburgh area. He also did a fair amount of black pipe air line installation and he taught me a trick to ensure air tight threaded fittings. I've been using this for years and have never had a single threaded fitting leak. There is a product you can get from large supply houses called X-pando. It's a type of hydraulic cement with additives. It comes in a can as a powder - mix a small amount to a peanut butter consistency and use it on the male threads and make the fitting. It expands to some ridiculous PSI and seals the joint almost permanently - to break apart 1/2" or 3/4" black pipe takes at least 24" wrenches. 1" takes a 36" and anything over that takes at least MAPP gas and the largest wrench you have with a long cheater bar.

    https://www.xpando.com/xpando.php

    I bought a 70 ounce can 40 years ago and still have 3/4 of it.

    18" threaded lines? Seems like a recipe for disaster. Every industrial installation I've been around used welded joints in anything 2" and above. That xpando might be fine for air lines since disassembly isn't often required. There are much better choices than pipe thread fittings these days. They do still have their place though.

  14. #29
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    For surface pipe, I like copper. It looks great & I enjoy working with it. I don't like to use PEX for surface work for the same reason I don't use BX for surface work. It just doesn't look very good no matter how careful you are with the installation.

    But galvanized pipe & threaded fittings is about the last choice for me.

  15. #30
    I didn't say he was doing 18" threaded lines - those don't even exist. Most pipe and fittings over6-8" are either welded or bolted via integral flanges. X-Pando is used on threaded fittings for both natural gas and compressed air. It can also be used for water and hydraulic lines. There is also a version for ultra-high pressure hydraulic systems (4,000 bar or 58,000 psi).

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