The warning system is great. most times if you have water it was pumped in when you brought fuel. Typically you might drive away from a station and some miles later the warning goes on.

I really try to stay away from low volume diesel fuel sellers. I even had to change a frozen fuel filter and thaw a frozen blockage in a low spot on the fuel line one winter.

Never ever buy fuel at a place that has a heater running at their pump in the winter. In most cases it is summer fuel that has gelled in their pump.