The deal is that you do a fuel check first flight of the day and after refuelling, and during that make sure you've pulled off any water that got in.
Job done. I recall years ago doing a course in a C150 in Florida where we always had to draw quite a lot of water off each afternoon following the daily thunderstorms. No big deal, and the aeroplanes ran fine.
Aircraft fuel tanks are designed with a sump, which is at the lowest point in the tank and where the drain is, and a draw off that's around half a gallon above that, for exactly these reasons. Unuseable fuel is at the bottom and where the water should settle.
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Last edited by Genghis the Engineer; 1st Jun 2013 at 10:22.