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I'm doing an at home experiment for my physics degree due to covid restrictions, and I need to suck water up a vertical tube. I would really appreciate any equipment recommendations or other advice you could give me, as I'm not very practical and I'm not sure how to put everything together to achieve what I want.

Let me describe the problem in detail. The bigger picture is that I want to put a vertical tube in a tank, draw water up the tube, then release the water so that it drops back down the tube and oscillates up and down within the tube. What I need to figure out is a cheap and simple way to draw the fluid up the tube initially.

The tube must be rigid, straight, and transparent. The tube will be about 1m in length, and I would like to be able to draw the fluid nearly to the top but not all the way to the top where it'd overflow. I must be able to draw the fluid slowly enough that I could precisely set the height anywhere in the tube. The tube diameter is not yet decided, but I would be happy to use standard sized pipes and fittings, ideally a tube between 0.5-2cm in diameter would be good (but I'm flexible on this).

I was thinking that I'd need to put a valve on the top of the tube, use a suction pump to draw water up the tube, then seal the valve, and when I'm ready to drop the fluid, quickly open the valve again. It would be a bonus (really not necessary if it's not very easy to incorporate) if I could get an accurate pressure measurement of the air inside the tube before I drop the fluid. Also, once I open the valve I don't want it to restrict air flow too much as this would stop the fluid falling freely. I want the pressure in the tube to near instantly reach atmospheric pressure after opening the valve.

I'd like to achieve all this for under £50 (ideally quite a bit less than that). I'm in the UK, so please could you recommend parts that I'd easily be able to obtain here.

(I suppose one alternative method is that I could pump water into the bottom of the tube, seal a valve at the top of the tube, then remove the pump apparatus from the bottom of the tube before opening the valve again.

I am aware I could also lower the tube into the tank, seal it, then lift it up, but this isn't viable for me as I won't have a deep enough tank to be able to get the water far enough up the tube.)

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  • $\begingroup$ What is the tube inside diameter and length? $\endgroup$
    – S. McGrew
    Jan 23 at 23:29
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Find a veterinarian to give you a syringe used on large animals. Drill a small hole in the side of the tube about an inch from the top, and fill it with silicone sealer. This will let you insert the needle of the syringe without leakage. Stretch a balloon tightly over the top of the tube. If need be, put a small funnel into the top of the tube (sealed with silicone sealer) so you can stretch the balloon better. Use the syringe to pull air out of the tube until the water reaches the desired height, then pop the balloon with a broken razor blade. Holding the tube in place amd measuring the oscillations is up to you!

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  • $\begingroup$ Thank you for your suggestion, it would have been a good idea! In the end, I was able to acquire quite a deep tank (70 cm tall cylindrical vase from IKEA), so I was able to " lower the tube into the tank, seal it, then lift it up" as I mentioned at the end of my question. $\endgroup$
    – Rational Function
    Mar 20 at 16:14

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