Mechta, water in the tank is always going to give a false reading in a capacitance system due to the two liquids having different dielectric values. The only pilot I know who had a problem with water in the tank said the gauge went to a max reading ie showing full tank.
Megan, if water in the fuel is always going to give a false reading on a capacitance gauge, I can't help wondering if this could have been a contributing factor to the Glasgow Police helicopter accident?
John Farley, fair point re passing the course!