pumping fuel through several filters to separate any water and to remove sludge, sediment, and biological organisms. Done to salvage a large quantity of contaminated fuel while simultaneously cleaning the fuel tank. The fuel is drawn from a tank by a hose directed into each corner, scrubbed, and then returned to the tank under pressure, which is used to power wash the tank’s interior. The filtering process is repeated until the fuel appears clean. Also known as fuel polishing.