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Thread: Rapidair which size?

  1. #16
    Dryer is just a dehumidifier.

  2. #17
    I have a 24 x 32 shop with a 1/2 inch line going 3/4 around the shop (front door is a 18 foot door so didn't need it there). Like others have mentioned - 1/2 inch seems completely sufficient. More fittings available at my local store for that size plus cheaper overall. Great product - no leaks after 3 years use - great investment.

  3. #18
    I installed rapid air 1/2" a few years ago, bought 2 sets, and it is fine for my shop. My air hose is 3/8", so why would I need a large line? And I have a single cylinder air compressor. It is even big enough to run my tire machine.

  4. #19
    Join Date
    May 2005
    Highland MI
    Blog Entries
    For running normal air tools up to a 1" rattle gun, 1/2" will be fine unless you have crazy long runs of pipe. The only thing I can think of that might need more air is a big sandblaster, but then your compressor will be the limiting factor. I just installed the 60 gallon Kobalt 3.7 hp compressor in my basement shop which cycles 135-175 psi. I come off the compressor with a 1/2" filter/regulator set at 120 psi so my system always sees 120 psi at the beginning of the run. After that I split to two runs of 3/8" rubber hose. Old school, but it works fine for me. I have a second regulator in the garage less than 10 feet away prior to my 3/8" hose reel that I typically keep at 100 psi.
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    NOW you tell me...

  5. #20
    Join Date
    Feb 2008
    E TN, near Knoxville
    Quote Originally Posted by Jim Andrew View Post
    My air hose is 3/8", so why would I need a large line?
    It wouldn't apply in your case but might help some people - a larger line acts like a reservoir to give a bit more volume. When constructing farm buildings far from power I put a portable pancake compressor near the power and ran 100s of feet of air line. We could operate several air guns a little longer before the compressor kicked in. Of course, it took a like longer to pump back up to pressure then. And since the volume of air has inertia, an application with a high demand can pull air from a larger line quickly with less pressure drop.

    I've read of some industrial installations where air was being used at several stations at once. The design used a larger diameter pipe connected in a ring configuration, a big loop. This way no user was at the end of the line and "Because air is supplied to any piece of equipment from two directions the velocity is halved and the pressure drop reduced." (From, pg 54-55) And from the CEATI Compressed Air Handbook: "A single loop of pipe can reduce pressure differential by 75% compared to a single pipe of similar size. Multiple loops can further enhance the flow of air."

    No need for this in my little shop!

    Last edited by Jim Becker; 09-06-2019 at 6:04 PM. Reason: fixed quote tagging

  6. #21
    Join Date
    Feb 2003
    Griswold Connecticut
    Quote Originally Posted by Jim Andrew View Post
    I installed rapid air 1/2" a few years ago, bought 2 sets, and it is fine for my shop. My air hose is 3/8", so why would I need a large line? And I have a single cylinder air compressor. It is even big enough to run my tire machine.

    Air friction losses and differential pressure drop across the actual hose itself.
    If you were to put a gauge at both ends of an air hose, you would see that they both have the same pressure indicated. At the moment the trigger is depressed on an air tool, the pressure closest to the tool will drop, and so will the pressure at the other end of the hose. It's almost an absolute guarantee that the pressure gauge closest to the tool will have a lower indicated pressure than the gauge at the other end. This is the representation of the inability for a smaller diameter hose, to pass enough air volume to maintain pressure.
    In real life, most people would never notice this drop. If you're running impact drivers that require high breakaway torques, you will. John has a farm,and I am fairly certain that if he's doing his own maintenance on tractors, back hoes, and front loaders, the breakaway torques he will need just to remove a wheel will exceed a 1000ft/lbs.
    Whenever I hear someone say that they need a 175psi air compressor, to run a 120psi air tool because "it works better". I am just about certain that there is a small diameter air hose, on a reel, somewhere in the equation.
    Most people will never see the need for a larger diameter hose. 1/2" airlines , a 3/8" hose, with 1/4" air fitting will do most everything a person would want.
    "The first thing you need to know, will likely be the last thing you learn." (Unknown)

  7. #22
    Join Date
    Sep 2016
    Modesto, CA, USA
    Your 1/2 pex is really 3/8 pipe size.

  8. #23
    Join Date
    Jan 2006
    Grand Forks, ND
    1\2" rapid air is what I have in my home shop, never had an issue. I dont like working with 3/4" as we have that at work. Much more durable than the 1/2" but for home use I'd just go with that. just my .02
    A bus station is where a bus stops. A train station is where a train stops. My desk is a work station.

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