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Water, Tube and Resistance

  1. Apr 16, 2012 #1
    Hello all,

    I've not posted in a long time, but I will start by thanking you for your input pertaining to my last posts (about ice). They were very helpful.

    I have a new small dilemma, and I hope you can give me some direction on how to resolve it.

    I have a small tray that collects water slowly. This tray is only a foot long and 2" deep.

    I've drilled a hole in the side of the tray (trying to attach a pic)http://www.biznet.net/images/capture.jpg [Broken] and I've inserted a 1/4" vinyl tube with an inner dimension of 0.17".

    The tube is inserted on the side (parallel to the table surface), so I don't know if that is causing the issue.

    The tube runs to the edge of a table, and then straight downwards. No rising before it goes downward.

    The tube will allow water to flow down it sometimes. and sometimes, no matter how deep the water gets, the water will not start flowing down the tube on its own unless I move it around.

    Is the problem the inner diameter, or is the problem that I have the tube inserted at the side and horizontal of an inch or so?

    I've tried this with black rubber tubing as well to see if it was the material. Same results.

    I thought that the water would simply drip out the side and down the tube gradually as needed, but that does not seem to be happening.

    Thank you in advance for any insight you might give.


    Last edited by a moderator: May 5, 2017
  2. jcsd
  3. Apr 17, 2012 #2


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    The tube will narrow considerably as it bends over the edge of the table.
    You could try stiffening it somehow so that the bend is more gradual.

    At these dimensions, there's not going to be much water pressure. A bubble in the tube could easily create an airlock, but I'd have thought you'd be able to see that. Can you see how far the water gets into the tube?
    You could try flushing a little detergent through the tube first.
  4. Apr 17, 2012 #3
    Thank you.

    Is there a minimum inner dimension that you know of that would make it work more reliably?

    Yes, we're trying to keep it as small as we can.

  5. Apr 17, 2012 #4


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    No, can't help with that. It would depend on the head pressure, i.e. the depth of water above the inlet. Make the inlet as close to the base of the tray as possible, and make the distance the tube has to go before heading downwards as short as possible. And as I said, make sure the inside of the tube is grease-free.
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