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Thread: Moisture in air compressor lines

  1. #1

    Question Moisture in air compressor lines

    HELP! I have neglected regular draining water or moisture from my air compressor tank. This needs to be a regular habit because now I am in a terrible situation. I drained my air tank but water is in the air lines I have run throughout my shop.
    After draining the tank, I have pushed air through the lines several minutes but blowing onto bare wood you can see the wood get wet. I must have a cheap"o water trap filter because it does not seem to be working very well.
    Two questions: 1.) How do I get the water/moister out of my installed lines throughout my shop because it does not seem to want to purge by running air through the line, and 2.) What is the ultimate Water trap filter to help keep water from "point of use" in the shop?

  2. The best way to keep moisture out of your lines is to open the valve at the bottom of your compressor to get rid of all air, at the end of each day. They also make special in line triple water traps, very expensive, that professionals use for air when they are spray painting. The ultimate is having an in-line heater that dries the air and is often used for CNC spindles that require air as part of the system. Oh, one more important thing: on every compressor there is a cock valve at the bottom side of the tank. There is also another plug at the very bottom of the tank. This is the one that should be plumbed for draining air.

    What I have done with my compressors is install an extension from the bottom part of the tank, add a ball valve so I can simply use my foot to kick it open after the compressor is shut off. Have hearing protection on, but you want that air pressure blowing off that wet air. If you put a towel in front of the valve opening, it will be soaked with rusted water! That's the moisture you want to get rid of so that any new moisture is from the "new" air when you fire up the compressor on the next use. good luck.

  3. #3
    Thank you. The moisture is drained from the tank now but water/moisture is still coming out my air nozzle at the end of the line. Continued running air through it for some minutes does not seem to decrease the moisture at this point. I am wondering if I need to allow gravity to drain water from my hose- OMG- that would be a lot of work due to the (more or less) permanent piping I have in the shop.

  4. #4
    Join Date
    Sep 2016
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    Modesto, CA, USA
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    Piping should run in a shallow slope up from compressor to each outlet. Each outlet should come off the top of the main line then turn down to a tee fitting where air comes out horizontal and there is a drip leg with a drain valve at the bottom. There should be a tee out of the compressor so all the drain back water goes down into a drip leg to be blown out from time to time.
    Bill D

  5. #5
    Join Date
    May 2009
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    black river falls wisconsin
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    i have same problem in winter. i ran my air lines in attick and wonder if that warm air is hitting cold pipes in the unheated attic and causing the probem for me... I drain my tank all time so not a buildup of water in tank.

  6. #6
    Join Date
    Nov 2003
    Location
    Central North Carolina
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    1,569
    A search on this site will find all kinds of information about getting moisture out of your air, and keeping it out.

    Warm air rises in the tank. Take air from the top of your air compressor tank and you will get the wettest air.

    Cooling the air with a refrigerated dryer will remove a lot of moisture from the air before it gets in the air lines.

    You could get a tank of Nitrogen and blow it slowly through your air lines. Being very dry, it will remove the moisture as it flows through the line.

    Sorry, but I'm tired of responding to these same questions every few months. Do a search and you will find more than enough information on this.


    Charley
    Last edited by Charles Lent; 01-14-2020 at 11:10 PM.

  7. #7
    Join Date
    Feb 2014
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    Lake Gaston, Henrico, NC
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    The only way I have been able to assure completely dry air was to install a refrigerated air dryer. I know that's not exactly an option for the average garage, or basement shop, but it works absolutely. I bought the latest one off CL for $125. It's way oversized for my 7-1/2 hp compressor, but any difference in electricity used is not noticed. There are all sorts of makeshift, complicated piping runs that are claimed to work, but I was never convinced by the theory.

    I never owned one of the water separating filters that worked very good, for very long, and that includes the oversized, expensive ones.

  8. #8
    Join Date
    Nov 2009
    Location
    Peoria, IL
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    If your water filter is located next to the compressor, it's useless. The warm air right at the compressor can hold a lot of moisture and get right past the filter. Locate a filter at the end of the line and it's way easier to remove the water from cooler air. As Bill said, slope your lines so with all the pressure off, the condensed water will flow back. You can get a paper filter that does well with line moisture. It's nickname is a toilet paper filter, but it uses a roll of brown paper. Not as cheap as they used to be, but very effective. There are also desiccant filters that you can recycle the desiccant by baking it in a toaster ove.

  9. #9
    I don't think I've ever been the last one out of a shop without draining the tank. And turning off the compressor.

  10. #10
    Join Date
    Mar 2014
    Location
    Tulsa, OK
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    179
    I have a fairly decent compressor, a Quincy. It came from the factory with a bleeder valve on one of the bottom feet, so it is easily accessed for water drainage. I built a small manifold out of 1/2" black pipe, reducers, T's, quick disconnects......
    I used the factory air-out location to come out 6", added a T, then added 8" of line going down so I could put a ball valve on that as well. The other side of that T goes up about a foot and into a 90* elbow. When I open the valves up to bleed off water I can usually drain water from both valves.
    Not sure just exactly how dry you need your system to be? You might need to add a dryer?$?$?
    If you live in a large metro then consulting a company that specializes in air-compressor sales and service might be a better option.

  11. #11
    Join Date
    Aug 2013
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    My compressor has a radiator type cooling system, a desiccant style dryer and and automatic tank bleeder (works on a timer). I also have a jog before the outlet at all machines and a water separator at each regulator. It’s the coolest driest and cleanest air system I’ve used.

    Im sure a similar setup could be retrofitted without much outlay.
    Bumbling forward into the unknown.

  12. #12
    Join Date
    Feb 2003
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    Griswold Connecticut
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    Quote Originally Posted by Bruce Bradford View Post
    HELP! I have neglected regular draining water or moisture from my air compressor tank. This needs to be a regular habit because now I am in a terrible situation. I drained my air tank but water is in the air lines I have run throughout my shop.
    After draining the tank, I have pushed air through the lines several minutes but blowing onto bare wood you can see the wood get wet. I must have a cheap"o water trap filter because it does not seem to be working very well.
    Two questions: 1.) How do I get the water/moister out of my installed lines throughout my shop because it does not seem to want to purge by running air through the line, and 2.) What is the ultimate Water trap filter to help keep water from "point of use" in the shop?
    Bruce
    Let's address the immediate problem.
    First, whatever you're using for a moisture filter is either saturated, or not working any longer. You have some filters to replace.
    Second. It will do little to no good to try and blow your lines dry if your compressor has either just finished cycling, or is cycling while you're blowing down the lines. If you're going to use the tank to blow down the lines, you have to wait for the moisture to condense first. It's going to take some time to accomplish this.
    Third You can evacuate the air lines by pulling a continuous vacuum on them. This requires quite a bit of experience and a vacuum pump rig.
    Right now your system is saturated from what you have detailed. You may have to break it down to get the moisture out. You can also make a large volume mechanical separator, but it is still going to take time.

    The "best way" to keep moisture out of a system is a multistep process. Mechanical separation, moisture filtration, condensate drip legs, refrigeration, etc.
    There is tons of information posted here on the forum by many members with a lot of experience in industrial air supply system. We have also received much input from the engineering folks here on system design. Look through this and change your system to a better setup.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  13. #13
    Join Date
    Dec 2008
    Location
    WV
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    3,682
    Same as Brian here. Aftercooler on the compressor takes you to 80% dry air. Auto tank drain (ours is a timer as well but I wish it ran at each compressor cycle instead). We then have a Hankinson refrigerated dry, followed by a Hankinson coallescing oil filter to catch any oil from the head.

    If you install an auto tank drain alone it would help a lot with your moisture issue even if your bleeding your tank nightly/daily. With any use you will still have a lot of water sitting in the tank after a day if your compressor runs much at all. There is some moisture that comes out of our auto drain every single time it cycles even if the compressor isnt running much.

    Our auto drain (factory installed) is 1/2" and even on the shortest blow down setting and the longest time interval (just 2-3 seconds every 45 minutes) it would #1 deafen you if you were nearby, or #2 give you a heart attack. I poked a hole through the concrete floor into a storm drain and bushed the 1/2" down to a piece of 1/4" stainless tubing with the tip mashed down even smaller and poked it through the floor. Now its almost silent and doesnt dump a mile of air out of the tank causing the compressor to cycle just because of the timed auto drain.

    If your using any volume of air a large desiccant dryer (cheaper) or refrigerated dryer is your best bet. Keeping your lines dry before the air leaves the immediate area of the compressor is the best solution. The effort to pitch air lines back to the source is an old tactic from before the days of clean/dry air though still great if you have the ability. But if your have wet air, pitched lines or not, your going to have wet air and even with a small water separator at each drop your air will still be wet though maybe dry enough for your work.

    By the time youve invested in filter/separators at every drop, and if you have steel lines that are rusting from the wet air, youve spent the money for a dryer.

    Put a dryer in the line, and you will just have to persevere until your lines dry out.
    Sometimes I just want to look at pretty pictures,... Thats when I go to the Turners Forum

  14. #14
    Thanks for all the guidance. I have plenty of suggestions on how to keep the air dry so I hav plenty of plumbing/rigging to do - then followed by breaking down the existing piping and getting the water out~ The idea of a vacuum seems best for now.
    Thank you all for your suggestions
    Much appreciated.

  15. #15
    Quote Originally Posted by Bruce Bradford View Post
    Thanks for all the guidance. I have plenty of suggestions on how to keep the air dry so I hav plenty of plumbing/rigging to do - then followed by breaking down the existing piping and getting the water out~ The idea of a vacuum seems best for now.
    Thank you all for your suggestions
    Much appreciated.
    Just remember it can take as much as 24 hours to vacuum system free of water. A few things I have learned, (1) slope lines away from compressor, (2) take air off the top of lines (3) have a drain on bottom of every take off (4) have a drain at end of the line (lowest point.) By sloping lines away from compressor, every air use forces moisture towards drain at the end of the line.

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