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I've made a 10m water level using two 5m lengths of clear 6mm internal diameter pipe joined in the middle with a proprietary tube connector. I looped the tube with both ends next to each other and the centre much lower. I filled the tubes with coloured water and made sure all the air bubbles escaped but the liquid fails to equalise in the two tubes! Both tubes are open to the atmosphere but the level in one is about 50mm above the other! I've repeated the filling procedure about 10 times now with the same result, any ideas?

Posted by Patrick Russell on


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The internal diameter is notional and if the two lengths you have used came from different production batches then their average internal diameter along the length of one half may be different to the other. The fact that there is such large ratio between the length of the tube and the internal diameter only makes matters worse.

You need ideally to source a single 10m length and to select a larger internal diameter to maximise accuracy: 10mm i/d will be better but if you can cope with the extra volume of liquid then 15mm or even 20mm will be much more accurate.

Posted on Jul 28, 2010


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