syphon

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Note added at 10 mins (2013-03-13 15:32:33 GMT)
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Rury są wykonane z polietylenu. Mają nawiercone specjalne otwory, mają też siatkę ochronną. Jak tłumaczy Małgorzata Wnuk, rura działa jak syfon - reguluje poziom wody w danym miejscu. - Te specjalne rury przelewowe umożliwią przepływ wody przez zaporę, a to skutecznie niweluje straty wyrządzane podtopieniami.
http://www.wprost.pl/ar/345165/Jak-rozladowac-napiecia-na-li...

...of piping to serve as a siphon to lower the water level in the beaver pond...
Beaver dam drain options: (a) pipe drain, (b) siphon pipe drain, (c) three log drain.
Automatic beaver dam water control "Beaver deceiver"
...instalation creates a siphon which will start to siphon water when the water in...
http://tinyurl.com/bv2fwok

The word siphon (from Ancient Greek: σίφων “pipe, tube”, also spelled syphon) is sometimes used to refer to a wide variety of devices that involve the flow of liquids through tubes – see siphon terminology – but in the narrower sense it refers specifically to a tube in an inverted U shape which causes a liquid to flow uphill, above the surface of the reservoir, without pumps, powered by the fall of the liquid as it flows down the tube under the pull of gravity, and is discharged at a level lower than the surface of the reservoir it came from.
http://en.wikipedia.org/wiki/Siphon

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Note added at 16 mins (2013-03-13 15:38:17 GMT)
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Można dać 'siphon pipe'.

...when the beavers aren't looking, a siphon pipe could be inserted under the dam that would allow enough water to drain.
http://tinyurl.com/b4o2l63