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Thread: water feature problem

  1. #1 water feature problem 
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    Hi guys, I came across an interesting problem recently while building a water feature out of an old kettle and a terracotta tub. I mounted the kettle at a 45 degree angle on a piece of pipe and had this feeding into the tub as per my rough drawing at: http://erickendall.gallery.netspace..../water-feature
    The return pipe to the resevior gave me the water level in the tub, but to make the whole unit look better and to stop leaves and debris going down the return, I made up a brass cap so the water would have to be drawn from below the water surface to get to the return. I thought this would work quite well, but after about 2 minutes of running the unit, it made a gurgling noise and then the water level dropped to nearly the bottom of the brass cap. I couldn’t believe it!! This happened a couple of times, so then I thought it may need some bleed holes near the top of the brass cap. I drilled three 3mm holes around the circumference near the top. Turning the unit on again I found it took a little longer, but it still did the above action. I then drilled another 3 in between the original holes. This fixed the problem, but I still have no idea what the physics are behind it. By the way, the kettle spout is about 12 mm diameter with the water coming out under gravity. Any ideas?


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  3. #2  
    Forum Junior Zitterbewegung's Avatar
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    Dec 2007
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    You created a vacuum using the metal cap as shown in your scetch. Like getting gas out of the tank of your car with some rubber tubing. Only when the water level fell below the lower rim of the brass cap. In order to prevent this I'd recommend drilling holes in the top of the caP or making some slits in the side wall.


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  4. #3  
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    Thanks for the reply. I guess that makes sense. Is there some maths I can apply to these functions?
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  5. #4  
    Forum Bachelors Degree
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    Zitterbewegung is quite correct. You had siphoning action taking place, and it is easily prevented by drilling a hole at the top of the brass cap.

    Since your only aim is prevention of this effect, no maths apply. We could amuse ourselves with some hydraulic engineering if siphoning action were your intention. Cheers.
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