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Thread: Draining condensate from air compressor

  1. #1
    Join Date
    Apr 2010
    Location
    Houston, Texas area
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    1,044

    Draining condensate from air compressor

    For the last 2 years I have been opening up the ball valve at the bottom of my 20 gallon IR air compressor tank to drain off any accumulated water. I had been contemplating an auto drain valve that opens on every cycle, but no water ever came out. Then I realized the valve isn't at he bottom of the rounded tank, its slightly higher than the lowest point, so I titled the tank and a bunch of water came out.

    The compressor is kept in conditioned space so, even though I am in south Texas, the AC is running almost year round, and heated a few weeks in the winter,

    So what do people do to maintain/properly drain these tanks? Tilt it all the time? What is the value of an auto drain if there is still water in the bottom of the tank below the valve height.
    Mark McFarlane

  2. #2
    Join Date
    Feb 2019
    Location
    Annapolis
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    59
    INHO, an auto drain is well worth the cost & effort to install. Some types will still allow some residual water pooling in the tank. My practice has been when installing an auto drain is to put sufficient piping between the tank & valve in an attempt to have any water pool in the piping between the valve & tank vice in the tank.

  3. #3
    Join Date
    Apr 2017
    Location
    Michigan
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    1,000
    The inside of a compressor tank will always be damp unless there is a dryer between it and the compressor. The difference between damp and a little water is insignificant.

    An auto drain is a fine idea. As an alternative you could put an extension on the valve handle so you don't have to bend down under the task to open it.

  4. #4
    Join Date
    Apr 2008
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    East Virginia
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    785
    Quote Originally Posted by Tom Bender View Post
    The inside of a compressor tank will always be damp unless there is a dryer between it and the compressor. The difference between damp and a little water is insignificant.

    An auto drain is a fine idea. As an alternative you could put an extension on the valve handle so you don't have to bend down under the task to open it.
    +1

    I suspect the tank is always going to be at least wet on its interior surface, with a RH of 100%, unless you completely drain the tank of water and let out all the compressed air every time you use it. The main thing you want to avoid is losing a lot of storage volume due to accumulated water.
    Last edited by Jacob Reverb; 11-14-2019 at 9:56 AM.

  5. #5
    So rust isn't the issue?

  6. #6
    Join Date
    Sep 2016
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    Modesto, CA, USA
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    3,325
    I have always wondered about the point of galvanized pipe used inside. Buried in dirt the zinc prevents exterior rust. But the inside, which is wet all the time, has no zinc whatsoever.
    Bil lD

  7. #7
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    50,644
    I have an IR automatic drain system on my compressor...it periodically exhausts just a little bit of air and with it, any condensate. The drain on my compressor (vertical tank) is at the very bottom of the tank...no place for anything to collect that wouldn't be blown out with the air. Remember, the auto drain attaches to the drain and the drain "should" be at the lowest point on the tank.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  8. #8
    Join Date
    Jan 2004
    Location
    Lewiston, Idaho
    Posts
    27,141
    Like Jim I have an automatic drain on my vertical 26 gallon air compressor.

    Why have one? Prevent or slow down the tank rusting out. I have an acquaintance who lives in a rural area nearby. In an effort to fight of the effects of aging every morning he walks 3 miles in the hilly area where he lives. One morning while walking by the home of his nearest neighbor he saw his neighbor had a garage fire. JR said in an effort to save some tools from the guys garage the two of them could barely roll his air compressor from the garage because it was filled with water. I worry more about the tank exploding after rust weakens the tank.
    Ken

  9. #9
    Join Date
    Jul 2016
    Location
    Lebanon, TN
    Posts
    512
    I have read treads, like this, with interest. I have a 20 gallon, 20 year old Sears compressor that I had never drained.

    It's lived with me from CT, MD, NJ, FL, TX and TX in an unheated or air conditioned garage.

    It's on all the time and set to 120psi. My pipes leak a little and it cycles a couple of times a day when not in real use.

    I decided to drain it, after reading a similar thread, so I wheeled it outside, expecting a gallon or two of water to come out.

    This is all I got, about 4 drops of rusty brown water.


  10. #10
    Join Date
    Mar 2016
    Location
    Exeter, CA
    Posts
    394
    Hopefully you got compressed air out with it. If not, it could very well be clogged with rust so that's all that came out. I don't use mine all that often so I always turn it off and drain it when done using it. Its an upright tank with a bottom drain, that I added some piping to and extended the valve out to the front so I didn't have to get under the tank to do it - back is getting old! ha Randy

  11. #11
    Join Date
    May 2014
    Location
    Alberta
    Posts
    1,209
    My air compressor at the shop is a 60 gallon vertical Ingersoll-Rand. I have it set up on a mezzanine. I wanted to install an auto drain but the one I purchased did not fit. I went to a local parts store and got plastic brake line and fittings and installed it with the line like 12' long so it hangs down to the floor. On the end I have a ball valve installed and simply hold it over the sink and drain without having to climb up to the mezzanine. Have always drained my compressors on a regular basis as well as change oil in them. Had a Bostich twin tank that is now 35 plus years old,sold it to one of my ex employees, he is still using it.

  12. #12
    Join Date
    Apr 2010
    Location
    Houston, Texas area
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    1,044
    Thanks everyone for your responses.

    The drain on my IR tank is near the bottom, but on the side as seen in pic below. There could be maybe 3/4" of accumulated water in the tank below the drain point.

    For the first ~two years of use I never got any water out opening the drain, until I tipped the tank last month. There is no plug at the exact bottom of the tank, just the valve in the picture.

    .IMG_4487.jpg

    The rust looking stains on the tank aren't surface rust, just splash from when I tipped the tank to drain it.

    So auto drain or manual drain, I can't get all the water out unless I manually tilt the tank. Maybe this 3/4" of water is nothing to worry about.
    Mark McFarlane

  13. #13
    Join Date
    Feb 2014
    Location
    Lake Gaston, Henrico, NC
    Posts
    4,349
    The first thing I do on my little compressors is to change that little butterfly valve to a ball valve. Those little valves can get clogged just with dirty water from inside the tank.

  14. #14
    I live in Texas. Hot and humid here! My first compressor lasted 20 years before rusting through. I very seldom drained it. We did put motor oil in the tank to make it last longer. Since we only used that compressor for farm work and not painting or woodworking the oil wasn't a problem. I now have a new shop compressor and I drain it every time I use it. My small Bostich pancake compressor gets drained about every other time.

  15. #15
    Join Date
    Apr 2008
    Location
    Edmonton, Canada
    Posts
    2,236
    I always drain (air and water) the tank after each day of use and leave the valve open. Next time I want to use the compressor close the valve and start it up.

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