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.
How long after refuelling do you have to wait for the water to settle, so you can remove the water, or at least test for the presence of the first to settle out?
During my PPL I was told there was no point checking if you re-fuelled just before flying. But I have always wondered...