" take on fuel, it is always a good idea to check the sumps/ low points, and that goes for jets too.
You may care to review this statement.
If you do a water drain check, immediately after fueling it's an excercise in futility as the fuel entering the tanks, will still be happily sloshing around and with it any water.
Hence the reason, as an engineer, it was always done after as much down time as possible....... to allow any water to sink to the botton of the tank and thus with the fuel in a stable, rather than turbulent condition.