Replacement Fuel Water Separator FS-1001 is a Replacement Fuel Water Separator from Fass. At FASS our 1st priority is to guarantee that only the purest quality fuel is delivered to your diesel engine. We achieve this by removing dirt, water and air through our 2 step filtration process while switching the fuel delivery process from a suction delivery to a pressure delivery, thus eliminating the possibility of reintroducing air back into the fuel after it has already been removed. With filtration being such an important process, we choose to use fuel filters that have a rating as low as three Micron, which provides superior protection from debris in your diesel fuel.