A fuel/water separator works by exploiting two physical differences between water and diesel: density (water is denser, so it falls) and surface tension (water beads up against fuel-soluble surfaces). Inside the separator housing, fuel flows through a pleated filter media that catches solid particles. Below or around the media, a coalescing element (typically a hydrophobic mesh or screen) causes suspended water droplets to merge into larger drops. Once the drops are heavy enough, gravity pulls them down into a sediment bowl at the bottom of the housing. The fuel itself, lighter and now particle-free, continues upward to the engine. The driver drains the sediment bowl manually at fuel stops by opening a petcock valve. Empty water out, watch for clean fuel coming through, close the valve.
Browse the Fuel Water Separators collection →