What is the purpose of a diesel fuel/water separator?
Diesel fuel has a background “humidity” of water that cannot be removed. Water that exists freely as an emulsion or as droplets, is a concern for fuel system components. Free water flowing at high velocity between highly polished valve seats and through fine nozzle orifices causes a wearing action that approaches that of abrasion. The presence of free water, especially with entrained air and various fuel components, causes corrosion of the finely mated surfaces. Fuel/water separator filters use chemically treated filter media to repel water which then settles by gravity to the bottom of the filter. Accumulated water can be drained from the filter during recommended service intervals if equipped with a drain valve or plug. Note that alcohol based diesel fuel additives may severely degrade fuel/water separator performance.
