Water in Fuel? When Do You Drain the Filter?

As others have mentioned - in about 500,000 miles of driving personal diesel vehicles I have never had the water sensor trigger. I always drain a bit of fuel from the separator into a glass jar at oil change time and look. I buy fuel at “top tier” suppliers from stations that turn good volume.

The high pressure common rail injection system on a modern engine is capable of smashing water present in the fuel into an emulsion. As mentioned there are fuel conditioners designed to allow this minute trace contamination to pass through the injectors without causing undue damage.